Method for manufacturing display device

ABSTRACT

It is an object of the present invention to provide a technique for manufacturing a highly reliable display device at low cost with high yield. A first electrode layer is formed by a sputtering method using a gas containing hydrogen or H 2 O, an electroluminescent layer is formed over the first electrode layer, and a second electrode layer is formed over the electroluminescent layer. According to one aspect of the present invention, a display device is manufactured to include a first electrode layer including indium zinc oxide containing silicon oxide and tungsten oxide, an electroluminescent layer over the first electrode layer, and a second electrode layer over the electroluminescent layer, where the electroluminescent layer includes a layer containing an organic compound and an inorganic compound to be in contact with the first electrode layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.11/382,420, filed May 9, 2006, now allowed, which claims the benefit ofa foreign priority application filed in Japan as Serial No. 2005-141899on May 13, 2005, both of which are incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for manufacturing a displaydevice.

2. Description of the Related Art

In recent years, a liquid crystal display device and anelectroluminescence display device, in which a thin film transistor(hereinafter also referred to as a TFT) is integrated over a glasssubstrate, have been developed. In each of these display devices, a thinfilm transistor is formed over a glass substrate by using a techniquefor forming a thin film, and a liquid crystal element or alight-emitting element (an electroluminescence element, hereinafter alsoreferred to as an EL element) is formed as a display element overvarious circuits composed of the thin film transistors so that thedevice functions as a display device.

A TFT and a display element are electrically connected to each other bystacking a pixel electrode of the display element and a wiring connectedto a source region or a drain region of the TFT. Further, in order totransmit light emitted from a display device, a light-transmittingelectrode is used as a pixel electrode (see, for example, the PatentDocument 1).

[Patent Document 1]

Japanese Patent Application Laid-Open No.: 2002-57162

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a technique formanufacturing a display device having high reliability and excellentelectric characteristics with high yield without complicating steps andapparatuses.

In the present invention, as a light-transmitting electrode, an indiumzinc oxide film containing tungsten oxide is formed by using a gascontaining an H₂O gas or an H₂ gas, and thus, a film can be obtained,which has high transmittance in a visible light region, low resistivity,and favorable processability. In addition, silicon oxide may becontained in the indium zinc oxide film containing tungsten oxide in thepresent invention. By using such a film for a pixel electrode of adisplay device, a highly reliable display device can be manufactured, inwhich light extraction efficiency of a light-emitting element isfavorable and defects due to an etching defect of an electrode or thelike are suppressed.

As a display device to which the present invention can be applied, alight-emitting display device is given, in which a light-emittingelement and a TFT are connected, where the light-emitting elementincludes a layer containing an organic material or an inorganic materialexhibiting light emission called electroluminescence (hereafter alsoreferred to as EL), or a mixture of an organic material and an inorganicmaterial interposed between electrodes. In addition, alight-transmitting electrode layer shown in the present invention canalso be applied to a liquid crystal display device using a liquidcrystal material as a display element.

According to one aspect of the present invention, a method formanufacturing a display device includes the steps of forming a firstelectrode layer by a sputtering method using a gas containing hydrogen,forming an electroluminescent layer over the first electrode layer, andforming a second electrode layer over the electroluminescent layer.

According to another aspect of the present invention, a method formanufacturing a display device includes the steps of forming a firstelectrode layer by a sputtering method using a gas containing water,forming an electroluminescent layer over the first electrode layer, andforming a second electrode layer over the electroluminescent layer.

According to another aspect of the present invention, a method formanufacturing a display device includes the steps of forming an indiumzinc oxide film containing tungsten oxide by a sputtering method using agas containing hydrogen, forming a first electrode layer by processingthe indium zinc oxide film containing tungsten oxide, forming anelectroluminescent layer over the first electrode layer, and forming asecond electrode layer over the electroluminescent layer.

According to another aspect of the present invention, a method formanufacturing a display device includes the steps of forming an indiumzinc oxide film containing tungsten oxide by a sputtering method using agas containing water, forming a first electrode layer by processing theindium zinc oxide film containing tungsten oxide, forming anelectroluminescent layer over the first electrode layer, and forming asecond electrode layer over the electroluminescent layer.

According to another aspect of the present invention, a method formanufacturing a display device includes the steps of forming an indiumzinc oxide film containing silicon oxide and tungsten oxide by asputtering method using a gas containing hydrogen, forming a firstelectrode layer by processing the indium zinc oxide film containingsilicon oxide and tungsten oxide, forming an electroluminescent layerover the first electrode layer, and forming a second electrode layerover the electroluminescent layer.

According to another aspect of the present invention, a method formanufacturing a display device includes the steps of forming an indiumzinc oxide film containing silicon oxide and tungsten oxide by asputtering method using a gas containing water, forming a firstelectrode layer by processing the indium zinc oxide film containingsilicon oxide and tungsten oxide, forming an electroluminescent layerover the first electrode layer, and forming a second electrode layerover the electroluminescent layer.

According to another aspect of the present invention, a method formanufacturing a display device includes the steps of forming a firstelectrode layer, forming an electroluminescent layer over the firstelectrode layer, and forming a second electrode layer over theelectroluminescent layer by a sputtering method using a gas containinghydrogen.

According to another aspect of the present invention, a method formanufacturing a display device includes the steps of forming a firstelectrode layer, forming an electroluminescent layer over the firstelectrode layer, and forming a second electrode layer over theelectroluminescent layer by a sputtering method using a gas containingwater.

According to another aspect of the present invention, a method formanufacturing a display device includes the steps of forming a firstelectrode layer, forming an electroluminescent layer over the firstelectrode layer, forming an indium zinc oxide film containing tungstenoxide over the electroluminescent layer by a sputtering method using agas containing hydrogen, and forming a second electrode layer byprocessing the indium zinc oxide film containing tungsten oxide.

According to another aspect of the present invention, a method formanufacturing a display device includes the steps of forming a firstelectrode layer, forming an electroluminescent layer over the firstelectrode layer, forming an indium zinc oxide film containing tungstenoxide over the electroluminescent layer by a sputtering method using agas containing water, and forming a second electrode layer by processingthe indium zinc oxide film containing tungsten oxide.

According to another aspect of the present invention, a method formanufacturing a display device includes the steps of forming a firstelectrode layer, forming an electroluminescent layer over the firstelectrode layer, forming an indium zinc oxide film containing siliconoxide and tungsten oxide over the electroluminescent layer by asputtering method using a gas containing hydrogen, and forming a secondelectrode layer by processing the indium zinc oxide film containingsilicon oxide and tungsten oxide.

According to another aspect of the present invention, a method formanufacturing a display device includes the steps of forming a firstelectrode layer, forming an electroluminescent layer over the firstelectrode layer, forming an indium zinc oxide film containing siliconoxide and tungsten oxide over the electroluminescent layer by asputtering method using a gas containing water, and forming a secondelectrode layer by processing the indium zinc oxide film containingsilicon oxide and tungsten oxide.

According to another aspect of the present invention, a display deviceincludes a first electrode layer including indium zinc oxide containingsilicon oxide and tungsten oxide, an electroluminescent layer over thefirst electrode layer, and a second electrode layer over theelectroluminescent layer, where the electroluminescent layer includes alayer containing an organic compound and an inorganic compound to be incontact with the first electrode layer.

According to another aspect of the present invention, a display deviceincludes a first electrode layer, an electroluminescent layer over thefirst electrode layer, and a second electrode layer including indiumzinc oxide containing silicon oxide and tungsten oxide over theelectroluminescent layer, where the electroluminescent layer includes alayer containing an organic compound and an inorganic compound to be incontact with the first electrode layer.

According to another aspect of the present invention, a display deviceincludes a conductive film having reflectivity, a first electrode layerincluding indium zinc oxide containing silicon oxide and tungsten oxideover the conductive film, an electroluminescent layer over the firstelectrode layer including indium zinc oxide containing silicon oxide andtungsten oxide, and a second electrode layer having a light-transmittingproperty over the electroluminescent layer, where the electroluminescentlayer includes a layer containing an organic compound and an inorganiccompound to be in contact with the first electrode layer.

By applying the present invention, a highly reliable display device canbe manufactured. Therefore, a high-definition and high-image qualitydisplay device can be manufactured with high yield.

These and other objects, features and advantages of the presentinvention will become more apparent upon reading of the followingdetailed description along with the accompanied drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIGS. 1A and 1B are views each illustrating a display device accordingto the present invention;

FIGS. 2A to 2D are views each illustrating a manufacturing method of adisplay device according to the present invention;

FIGS. 3A to 3C are views each illustrating a manufacturing method of adisplay device according to the present invention;

FIGS. 4A and 4B are views each illustrating a manufacturing method of adisplay device according to the present invention;

FIGS. 5A to 5C are views each illustrating a manufacturing method of adisplay device according to the present invention;

FIGS. 6A and 6B are views each illustrating a manufacturing method of adisplay device according to the present invention;

FIGS. 7A and 7B are views each illustrating a manufacturing method of adisplay device according to the present invention;

FIG. 8 is a view illustrating a display device according to the presentinvention;

FIG. 9 is a view illustrating a display device according to the presentinvention;

FIG. 10 is a view illustrating a display device according to the presentinvention;

FIGS. 11A and 11B are views each illustrating a display device accordingto the present invention;

FIG. 12 is a view illustrating a display device according to the presentinvention;

FIGS. 13A to 13C are views each illustrating a manufacturing method of adisplay device according to the present invention;

FIG. 14 is an equivalent circuit diagram of a display device that willbe described in FIG. 15;

FIG. 15 is a top view illustrating a display device according to thepresent invention;

FIGS. 16A to 16C are top views of a display device according to thepresent invention;

FIGS. 17A and 17B are top views of a display device according to thepresent invention;

FIGS. 18A to 18D are views each illustrating a structure of alight-emitting element which can be applied to the present invention;

FIGS. 19A to 19D are views illustrating electronic devices to which thepresent invention is applied;

FIGS. 20A and 20B are views illustrating electronic devices to which thepresent invention is applied;

FIGS. 21A and 21B are views each illustrating an electronic device towhich the present invention is applied;

FIG. 22 is a view illustrating an electronic device to which the presentinvention is applied;

FIG. 23 is a block diagram showing a main structure of an electronicdevice to which the present invention is applied;

FIG. 24 is a view illustrating a droplet-discharge method which can beapplied to the present invention;

FIG. 25 is a SEM photograph of a sample shown in Embodiment 1;

FIG. 26 is a SEM photograph of a sample shown in Embodiment 1;

FIG. 27 is a graph showing resistivity data with respect to H₂O gas flowrate of a sample shown in Embodiment 1;

FIG. 28 is a graph showing transmittance data of a sample shown inEmbodiment 1;

FIGS. 29A to 29 C are views each illustrating a structure of alight-emitting element which can be applied to the present invention;and

FIGS. 30A to 30C are views each illustrating a structure of alight-emitting element which can be applied to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Embodiment Modes of the present invention will be described in detailwith reference to the accompanying drawings. It is to be noted that thepresent invention is not limited to a following description, and it isto be easily understood by those skilled in the art that modes anddetails thereof can be modified in various ways without departing fromthe spirit and the scope of the invention. Therefore, the presentinvention should not be interpreted as being limited to the descriptionof the embodiment modes to be given below. Further, in the structure ofthe present invention, the same reference numerals are used for the sameportions or portions having the same functions in different drawings,and a repeated explanation thereof will be omitted.

Embodiment Mode 1

A method for manufacturing a display device in this embodiment mode willbe described in detail with reference to FIGS. 1A and 1B, 2A to 2D, 3Ato 3C, 4A and 4B, 5A to 5C, 6A and 6B, 10, 16A to 16C, 17A and 17B, 18Ato 18D, and 24.

FIG. 16A is a top view showing a structure of a display panel inaccordance with the present invention, which includes a pixel portion2701 in which pixels 2702 are arranged in matrix, a scanning line inputterminal 2703, and a signal line input terminal 2704 over a substrate2700 having an insulated surface. The number of pixels may be setdepending on various standards, for example, 1024×768×3 (RGB) in a caseof XGA, 1600×1200×3 (RGB) in a case of UXGA, and 1920×1080×3 (RGB) in acase of the use for a full spec high vision display.

The pixels 2702 are arranged in matrix by intersecting a scanning lineextending from the scanning line input terminal 2703 and a signal lineextending from the signal line input terminal 2704. Each of the pixels2702 is provided with a switching element and a pixel electrode layerconnected thereto. A typical example of the switching element is a TFT.A gate electrode layer side of the TFT is connected to the scanningline, and a source or drain side of the TFT is connected to the signalline, and thus, each pixel can be controlled independently by a signalinputted from the outside.

A TFT includes a semiconductor layer, a gate insulating layer and a gateelectrode layer as its major components. Wiring layers connected to asource region and a drain region formed in the semiconductor layer arefurther provided. Typically known are a top gate structure in which, asemiconductor layer, a gate insulating layer, and a gate electrode layerare provided in this order from a substrate side, a bottom gatestructure in which a gate electrode layer, a gate insulating layer, anda semiconductor layer are provided in this order from a substrate side,and the like, and the present invention may employ any of thesestructures.

FIG. 16A shows a structure of a display panel in which a signal to beinputted to the scanning line and the signal line is controlled by anexternal driver circuit; however, a driver IC 2751 may also be mountedover the substrate 2700 by a COG (Chip On Glass) method as shown in FIG.17A. Further, as another mode, a TAB (Tape Automated Bonding) method asshown in FIG. 17B may also be employed. A driver IC may be formed over asingle crystal semiconductor substrate or a glass substrate by using aTFT. In FIGS. 17A and 17B, the driver IC 2751 is connected to an FPC(Flexible Printed Circuit) 2750.

Further, in a case of forming a TFT provided in a pixel by using acrystalline semiconductor, a scanning line driver circuit 3702 may beformed over a substrate 3700 as shown in FIG. 16B. In FIG. 16B, a pixelportion 3701 is controlled by an external driver circuit, to which asignal line input terminal 3704 is connected, similarly to FIG. 16A. Ina case of forming a TFT provided in a pixel by using a polycrystalline(microcrystalline) semiconductor, a single crystal semiconductor and thelike with high mobility, a pixel portion 4701, a scanning line drivercircuit 4702, and a signal line driver circuit 4704 can be formed to beintegrated over a substrate 4700 as shown in FIG. 16C.

As shown in FIG. 2A, over a substrate 100 having an insulated surface,as a base film, a base film 101 a is formed by using a silicon nitrideoxide (SiNO) film to be 10 to 200 nm thick (preferably, 50 to 100 nmthick) and a base film 101 b is stacked thereover by using a siliconoxynitride (SiON) film to be 50 to 200 nm thick (preferably, 100 to 150nm thick) by a sputtering method, a PVD method (Physical VaporDeposition), a CVD method (Chemical Vapor Deposition) such as a lowpressure CVD method (LPCVD method) or a plasma CVD method, or the like.Alternatively, acrylic acid, methacrylic acid, or a derivative thereof,a heat-resistant high-molecular material such as polyimide, aromaticpolyamide, or polybenzimidazole, or a siloxane resin may be used.Further, the following resin material may also be used: a vinyl resinsuch as poly(vinyl alcohol) or poly(vinyl butyral), an epoxy resin, aphenol resin, a novolac resin, an acrylic resin, a melamine resin, anurethane resin, or the like. In addition, an organic material such asbenzocyclobutene, parylene, fluorinated arylene ether, or polyimide; acomposite material containing a water-soluble homopolymer and awater-soluble copolymer; or the like may be used. As a method, adroplet-discharge method, a printing method (a method for forming apattern, such as screen printing or offset printing), a coating methodsuch as a spin coating method, a dipping method, or the like may also beused. In this embodiment mode, the base films 101 a and 101 b are formedby a plasma CVD method. The substrate 100 may be a glass substrate, aquartz substrate, a silicon substrate, a metal substrate, or a stainlesssteel substrate having a surface covered with an insulating film.Further, a plastic substrate having a heat resistant property or aflexible substrate such as a film which can resist a processingtemperature of this embodiment mode may also be used. As a plasticsubstrate, a substrate formed of PET (polyethylene terephthalate), PEN(polyethylene naphthalate), or PES (polyether sulfone) may be used, andas a flexible substrate, a synthetic resin such as acrylic can be used.Since a display device manufactured in this embodiment mode has astructure in which light from a light-emitting element is extractedthrough the substrate 100, the substrate 100 is required to have alight-transmitting property.

As the base film, silicon oxide, silicon nitride, silicon oxynitride,silicon nitride oxide and the like may be used in a single layerstructure or a stacked structure of two or three layers. It is to benoted that, in this specification, silicon oxynitride is a substance inwhich the composition ratio of oxygen is higher than that of nitrogenand can also be referred to as silicon oxide containing nitrogen.Similarly, silicon nitride oxide is a substance in which the compositionratio of nitrogen is higher than that of oxygen and can also be referredto as silicon nitride containing oxygen. In this embodiment mode, overthe substrate, a silicon nitride oxide film is formed to be 50 nm thickusing SiH₄, NH₃, N₂O, N₂, and H₂ as a reaction gas, and a siliconoxynitride film is formed to be 100 nm thick using SiH₄ and N₂O as areaction gas. Further, the silicon nitride oxide film may be formed tobe 140 nm thick and the silicon oxynitride film to be stacked may beformed to be 100 nm thick.

Subsequently, a semiconductor film is formed over the base film. Thesemiconductor film may be formed by a sputtering method, an LPCVDmethod, a plasma CVD method or the like to be 25 to 200 nm thick(preferably, 30 to 150 nm thick). In this embodiment mode, it ispreferable to use a crystalline semiconductor film formed bycrystallizing an amorphous semiconductor film by laser irradiation.

A material for forming the semiconductor film can be an amorphoussemiconductor (hereinafter also referred to as “AS”) formed by a vapordeposition method or a sputtering method by using a semiconductormaterial gas typified by silane or germane, a polycrystallinesemiconductor formed by crystallizing the amorphous semiconductor byusing light energy or thermal energy, a semi-amorphous semiconductor(also referred to as microcrystal and hereinafter also referred to as“SAS”), or the like.

An SAS is a semiconductor having an intermediate structure betweenamorphous and crystalline (including single crystal and polycrystalline)structures and a third state which is stable in free energy. Moreover,an SAS includes a crystalline region with a short-distance order andlattice distortion. A crystal grain having a diameter of 0.5 to 20 nmcan be observed at least in a portion of a film. In a case of containingsilicon as a main component, Raman spectrum is shifted to the wavenumber side lower than 520 cm⁻¹. The diffraction peaks of (111) and(220), which are believed to be derived from silicon crystal lattice,are observed by X-ray diffraction. An SAS contains hydrogen or halogenby at least 1 atomic % or more for terminating dangling bonds. An SAS isformed by glow discharge decomposition (plasma CVD) of a gas containingsilicon. As the gas containing silicon, SiH₄ can be used, and inaddition, Si₂H₆, SiH₂Cl₂, SiHCl₃, SiCl₄, SiF₄ and the like can also beused. Further, F₂ and GeF₄ may be mixed. The gas containing silicon maybe diluted with H₂, or H₂ and one or a plurality of rare gas elementsselected from He, Ar, Kr, and Ne. The dilution ratio is 1:2 to 1:1000,pressure is approximately 0.1 to 133 Pa, and power supply frequency is 1to 120 MHz, preferably, 13 to 60 MHz. A temperature for heating thesubstrate is preferably 300° C. or lower, and an SAS can also be formedat 100 to 200° C. It is preferable that a concentration of impurities ofatmospheric components such as oxygen, nitrogen, and carbon as impurityelements in the film be 1×10²⁰ cm⁻³ or lower. In particular, an oxygenconcentration is preferably 5×10¹⁹/cm⁻³ or lower, and more preferably,1×10¹⁹/cm⁻³ or lower. Further, when a rare gas element such as helium,argon, krypton, or neon is contained to further increase the latticedistortion, stability can be enhanced, and a favorable SAS can beobtained. Further, as the semiconductor film, an SAS layer formed byusing a hydrogen-based gas may be stacked over an SAS layer formed byusing a fluorine-based gas.

As an amorphous semiconductor, hydrogenated amorphous silicon may betypically used while polysilicon and the like may be typically used as acrystalline semiconductor. Polysilicon (polycrystalline silicon)includes so-called high temperature polysilicon formed by usingpolysilicon as a main material, which is formed at a processingtemperature of 800° C. or higher; so-called low temperature polysiliconformed by using polysilicon as a main material, which is formed at aprocessing temperature of 600° C. or lower; polysilicon crystallized byadding an element which promotes crystallization; and the like. It isneedless to say that a semi-amorphous semiconductor or a semiconductorcontaining a crystal phase in a portion of a semiconductor film may alsobe used as described above.

In a case of using a crystalline semiconductor film for thesemiconductor film, the crystalline semiconductor film may be formed byvarious methods such as a laser crystallization method, a thermalcrystallization method, and a thermal crystallization method using anelement such as nickel which promotes crystallization. Further, amicrocrystalline semiconductor that is an SAS may be crystallized bylaser irradiation to enhance crystallinity. In a case where an elementwhich promotes crystallization is not used, before irradiating theamorphous semiconductor film with laser light, the amorphoussemiconductor film is heated for one hour in a nitrogen atmosphere at500° C. to discharge hydrogen so that a hydrogen concentration in theamorphous semiconductor film becomes 1×10²⁰ atoms/cm³ or lower. This isbecause, if the amorphous semiconductor film contains much hydrogen, theamorphous semiconductor film may be broken by laser light irradiation.Heat treatment for crystallization may be performed by using a heatingfurnace, laser irradiation, irradiation of light emitted from a lamp(also referred to as a lamp annealing), or the like. As a heatingmethod, an RTA method such as a GRTA (Gas Rapid Thermal Anneal) methodor an LRTA (Lamp Rapid Thermal Anneal) method may be used.

A method for introducing a metal element into the amorphoussemiconductor film is not particularly limited as long as it is a methodfor introducing the metal element over a surface of or inside theamorphous semiconductor film. For example, a sputtering method, a CVDmethod, a plasma treatment method (including a plasma CVD method), anabsorption method, or a method of coating a solution of metal salt canbe used. Among them, a method of using a solution is simple andadvantageous in that the concentration of the metal element can beeasily controlled. At this time, it is desirable to form an oxide filmby UV light irradiation in an oxygen atmosphere, a thermal oxidationmethod, treatment with ozone water containing hydroxyl radical orhydrogen peroxide, or the like to improve wettability of the surface ofthe amorphous semiconductor film so as to diffuse an aqueous solutionover the entire surface of the amorphous semiconductor film.

In order to obtain crystals having a large grain size, a continuous wavesolid state laser is used, and irradiation of laser light of a second tofourth harmonic of the fundamental wave is performed. Typically, asecond harmonic (532 nm) or a third harmonic (355 nm) of an Nd:YVO₄laser (fundamental wave is 1064 nm) is desirably used. Specifically,laser light of the continuous wave YVO₄ laser is converted into aharmonic by using a non-linear optical element, thereby obtaining laserlight having output of several W or more. It is preferable to form laserlight into a rectangular or elliptical shape on an irradiated surface byan optical system for irradiating the semiconductor film. An energydensity at this time is required to be about 0.001 to 100 MW/cm²(preferably, 0.1 to 10 MW/cm²). The semiconductor film is irradiatedwith the laser light at a scanning rate of about 05 to 2000 cm/sec(preferably 10 to 200 cm/sec).

It is preferable that a shape of a laser beam be linear. Accordingly,throughput can be improved. Further, the semiconductor film may beirradiated with laser at an incident angle θ (0<θ<90°) with respect tothe semiconductor film, thereby preventing an interference of the laser.

By scanning such laser and the semiconductor film relatively, laserirradiation can be performed. Further, in the laser irradiation, amarker may be formed to overlap beams with high precision and controlpositions for starting and finishing laser irradiation. The marker maybe formed over the substrate at the same time when an amorphoussemiconductor film is formed.

It is to be noted that the laser may be a continuous wave or pulsed gaslaser, solid state laser, copper vapor laser, gold vapor laser, or thelike. The gas laser includes an excimer laser, an Ar laser, a Kr laser,a He—Cd laser, and the like while the solid state laser includes a YAGlaser, a YVO₄ laser, a YLF laser, a YAlO₃ laser, a Y₂O₃ laser, a glasslaser, a ruby laser, an alexandrite laser, a Ti: sapphire laser, and thelike.

The laser crystallization may be performed by a pulsed laser at arepetition rate of 0.5 MHz or higher, which is a drastically higherrange of repetition rates than a generally used range of repetitionrates of several ten to several hundred Hz. It is said that the timebetween irradiation of laser light to the semiconductor film andcomplete solidification of the semiconductor film is several ten toseveral hundred nsec in a pulsed laser. Therefore, the semiconductorfilm can be irradiated with the following pulsed laser light during theperiod from melting of the semiconductor film by laser light tosolidification of the semiconductor film by using the foregoing range ofrepetition rates, Hence, since a solid-liquid interface can becontinuously moved in the semiconductor film, a semiconductor filmhaving crystal grains that have grown continuously in the scanningdirection is formed. Specifically, an aggregate of crystal grains havinga width of 10 to 30 μm in the scanning direction and a width of about 1to 5 μm in a direction perpendicular to the scanning direction can beformed. By forming crystal grains of a single crystal extended longalong the scanning direction, a semiconductor film which has almost nocrystal boundary at least in a channel direction of a thin filmtransistor can be formed.

The semiconductor film may be irradiated with laser light in an inertgas atmosphere such as a rare gas or nitrogen as well. Accordingly,roughness of the surface of the semiconductor film can be prevented bylaser irradiation, and variation of a threshold voltage due to variationof interface state density can be prevented.

An amorphous semiconductor film may be crystallized by a combination ofheat treatment and laser light irradiation, or one of heat treatment andlaser light irradiation may be performed plural times.

In this embodiment mode, a crystalline semiconductor film is formed byforming an amorphous semiconductor film over the base film 101 b andcrystallizing the amorphous semiconductor film. As the amorphoussemiconductor film, amorphous silicon formed by using a reaction gas ofSiH₄ and H₂ is used. In this embodiment mode, the base films 101 a and101 b, and the amorphous semiconductor film are continuously formed bychanging a reaction gas without breaking vacuum in the same chamber atthe same temperature of 330° C.

After removing an oxide film formed over the amorphous semiconductorfilm, an oxide film is formed to be 1 to 5 nm thick by UV lightirradiation in an oxygen atmosphere, a thermal oxidization method,treatment with ozone water containing hydroxyl radical or hydrogenperoxide solution, or the like. In this embodiment mode, Ni is used asan element which promotes crystallization. An aqueous solutioncontaining 10 ppm of nickel acetate is coated by a spin coating method.

In this embodiment mode, after performing heat treatment by an RTAmethod at 750° C. for three minutes, the oxide film formed over thesemiconductor film is removed and laser irradiation is performed. Theamorphous semiconductor film is crystallized by the aforementionedcrystallization treatment to form the crystalline semiconductor film.

In a case of performing crystallization by using a metal element, agettering step is performed to reduce or remove the metal element. Inthis embodiment mode, the metal element is captured by using anamorphous semiconductor film as a gettering sink. First, an oxide filmis formed over the crystalline semiconductor film by UV lightirradiation in an oxygen atmosphere, a thermal oxidation method,treatment with ozone water containing hydroxyl radical or hydrogenperoxide, or the like. The oxide film is preferably made thick by heattreatment. Then, the amorphous semiconductor film is formed to be 50 nmthick by a plasma CVD method (a condition of this embodiment mode: 350 Wand 35 Pa).

Thereafter, heat treatment is performed at 744° C. for three minutes byan RTA method to reduce or remove the metal element. Heat treatment mayalso be performed in a nitrogen atmosphere. Then, the amorphoussemiconductor film as a gettering sink and an oxide film formed over theamorphous semiconductor film are removed by hydrofluoric acid or thelike, thereby obtaining a crystalline semiconductor film 102 in whichthe metal element is reduced or removed (see FIG. 2A). In thisembodiment mode, the amorphous semiconductor film as a gettering sink isremoved by using TMAH (Tetramethyl Ammonium Hydroxide).

The semiconductor film obtained as described above may be doped with aslight amount of impurity elements (boron or phosphorus) for controllinga threshold voltage of a thin film transistor. This doping of impurityelements may be performed to the amorphous semiconductor film before thecrystallization step. When the amorphous semiconductor film is dopedwith impurity elements, the impurities can also be activated bysubsequent heat treatment for crystallization. Further, a defect and thelike caused in doping can be improved as well.

Subsequently, the crystalline semiconductor film 102 is processed into adesired shape by using a mask. In this embodiment mode, after removingan oxide film formed over the crystalline semiconductor film 102,another oxide film is formed. Then, a photo mask is formed, andsemiconductor layers 103, 104, 105, and 106 are formed by processingwith a photolithography method.

An etching process may employ either plasma etching (dry etching) or wetetching. In a case of processing a large area substrate, plasma etchingis more suitable. As an etching gas, a fluorine based gas or a chlorinebased gas such as CF₄, NF₃, Cl₂, or BCl₃ is used, to which an inert gassuch as He or Ar may be appropriately added. When an etching process byatmospheric pressure discharge is employed, local electric discharge canalso be realized, which does not require a mask layer to be formed overthe entire surface of the substrate.

In the present invention, a conductive layer for forming a wiring layeror an electrode layer, a mask layer for forming a predetermined pattern,or the like may be formed by a method capable of selectively forming apattern, such as a droplet-discharge method. In the droplet-discharge(eject) method (also referred to as an inkjet method in accordance withthe system thereof), liquid of a composition prepared for a specificpurpose is selectively discharged (ejected) to form a predeterminedpattern (a conductive layer, an insulating layer, or the like). At thattime, treatment for controlling wettability or adhesion may be performedin a formation region. Additionally, a method for transferring ordescribing a pattern, for example, a printing method (a method forforming a pattern such as screen printing or offset printing) or thelike can also be used.

In this embodiment mode, a resin material such as an epoxy resin, anacrylic resin, a phenol resin, a novolac resin, a melamine resin, or aurethane resin is used as a mask to be used. Alternatively, an organicmaterial such as benzocyclobutene, parylene, fluorinated arylene ether,or polyimide having a light transmitting property; a compound materialformed by polymerization of siloxane-based polymers or the like; acomposition material containing a water-soluble homopolymer and awater-soluble copolymer; and the like can also be used. In addition, acommercially available resist material including a photosensitive agentmay also be used. For example, it is possible to use a typical positiveresist, namely, a novolac resin and a naphthoquinonediazide compoundthat is a photosensitive agent; or a negative resist, namely, a baseresin, diphenylsilanediol, and an acid generating agent. When adroplet-discharge method is used, the surface tension and the viscosityof a material are appropriately adjusted by controlling the solventconcentration, adding a surfactant, and the like.

The oxide film over the semiconductor layer is removed, and a gateinsulating layer 107 covering the semiconductor layers 103, 104, 105,and 106 is formed. The gate insulating layer 107 is formed of aninsulating film containing silicon in a thickness of 10 to 150 nm by aplasma CVD method, a sputtering method, or the like. The gate insulatinglayer 107 may be formed by using a material such as an oxide material ornitride material of silicon, typified by silicon nitride, silicon oxide,silicon oxynitride, and silicon nitride oxide, and may have a stackedlayer structure or a single layer structure. Further, the insulatinglayer may be a stacked layer of three layers including a silicon nitridefilm, a silicon oxide film, and a silicon nitride film. A single layeror a stacked layer of two layers of a silicon oxynitride film may beemployed as well. Preferably, a silicon nitride film with dense filmquality may be used. A thin silicon oxide film may be formed between thesemiconductor layer and the gate insulating layer, in a thickness of 1to 100 nm, preferably 1 to 10 nm, and more preferably 2 to 5 nm. As amethod for forming a thin silicon oxide film, the surface of thesemiconductor region is oxidized by a GRTA method, an LRTA method, orthe like to form a thermal oxide film, thereby forming a silicon oxidefilm in a thin thickness. It is to be noted that a rare gas element suchas argon may be contained in a reaction gas and be mixed into aninsulating film to be formed in order to form a dense insulating filmhaving little gate leak current at a low film formation temperature. Inthis embodiment mode, a silicon oxynitride film is formed to be 115 nmthick as the gate insulating layer 107.

Subsequently, a first conductive film 108 having a thickness of 20 to100 nm and a second conductive film 109 having a thickness of 100 to 400nm, each of which serves as a gate electrode layer, are stacked over thegate insulating layer 107 (see FIG. 2B). The first conductive film 108and the second conductive film 109 can be formed by a sputtering method,an evaporation method, a CVD method, or the like. The first conductivefilm 108 and the second conductive film 109 may be formed of an elementselected from tantalum (Ta), tungsten (W), titanium (Ti), molybdenum(Mo), aluminum (Al), copper (Cu), chromium (Cr), and neodymium (Nd), oran alloy material or compound material having the element as a maincomponent. A semiconductor film typified by a polycrystalline siliconfilm that is doped with an impurity element such as phosphorus or anAgPdCu alloy may also be used as the first conductive film 108 and thesecond conductive film 109. The conductive film is not limited to thetwo-layer structure, and for example, may have a three-layer structurein which a tungsten film of 50 nm thick as a first conductive film, analuminum-silicon alloy (Al—Si) film of 500 nm thick as a secondconductive film, and a titanium nitride film of 30 nm thick as a thirdconductive film are sequentially stacked. In a case of the three-layerstructure, tungsten nitride may be used instead of tungsten as the firstconductive film; an aluminum-titanium alloy (Al—Ti) film may be usedinstead of an aluminum-silicon (Al—Si) alloy film as the secondconductive film; or a titanium film may be used instead of a titaniumnitride film as the third conductive film as well. Further, asingle-layer structure may also be used. In this embodiment mode,tantalum nitride (TaN) of 30 nm thick is formed as the first conductivefilm 108 and tungsten (W) of 370 nm thick is formed as the secondconductive film 109.

Then, masks 110 a, 110 b, 110 d, 110 e and 110 f are formed of a resistby a photolithography method, and the first conductive film 108 and thesecond conductive film 109 are processed into a desired shape to formfirst gate electrode layers 121, 122, 124, 125 and 126, and conductivelayers 111, 112, 114, 115, and 116 (see FIG. 2C). The first gateelectrode layers 121, 122, 124, 125, and 126, and the conductive layers111, 112, 114, 115, and 116 can be etched to have a desired taper shapeby appropriately adjusting an etching condition (the amount of electricpower applied to a coil-shaped electrode, the amount of electric powerapplied to an electrode on a substrate side, an electrode temperature ona substrate side, and the like) by an ICP (Inductively Coupled Plasma)etching method. Further, an angle and the like of the taper shape canalso be controlled by the shapes of the masks 110 a, 110 b, 110 d, 110 eand 110 f. As an etching gas, a chlorine based gas typified by Cl₂,BCl₃, SiCl₄, CCl₄, or the like, a fluorine based gas typified by CF₄,SF₆, NF₃, or the like, or O₂ can be appropriately used. In thisembodiment mode, the second conductive film 109 is etched using anetching gas containing CF₄, Cl₂, and O₂, and then, the first conductivefilm 108 is continuously etched using an etching gas containing CF₄ andCl₂.

Subsequently, the conductive layers 111, 112, 114, 115, and 116 areprocessed into a desired shape using the masks 110 a, 110 b, 110 d, 110e and 110 f. At this time, the conductive layers are etched with anetching condition of high selection ratio of the second conductive film109 which forms the conductive layers with respect to the firstconductive film 108 which forms the first gate electrode layers. By thisetching, the conductive layers 111, 112, 114, 115, and 116 are etched toform second gate electrode layers 131, 132, 134, 135, and 136. In thisembodiment mode, the second gate electrode layers also have a tapershape, in which a taper angle is larger than that of the first gateelectrode layers 121, 122, 124, 125, and 126. It is to be noted that thetaper angle is an angle of the side surface with respect to the surfaceof the first gate electrode layer, the second gate electrode layer, andthe conductive layer. Accordingly, when the taper angle is increased to90°, the conductive layer has a perpendicular side surface. In thisembodiment mode, the second gate electrode is formed by using an etchinggas of Cl₂, SF₆, and O₂.

In this embodiment mode, each of the first gate electrode layers, theconductive layers, and the second gate electrode layers is formed tohave a taper shape, and thus, both of the two gate electrode layers havetaper shapes. However, the present invention is not limited thereto, andone of the gate electrode layers may have a taper shape while the otherhas a perpendicular side surface by anisotropic etching. As described inthis embodiment mode, the taper angles may be different or the samebetween the stacked gate electrode layers. With a taper shape, coverageof a film to be stacked thereover is improved and a defect is reduced,and thus, reliability is enhanced.

Through the aforementioned steps, a gate electrode layer 117 formed ofthe first gate electrode layer 121 and the second gate electrode layer131, and a gate electrode layer 118 formed of the first gate electrodelayer 122 and the second gate electrode layer 132 can be formed in aperipheral driver circuit region 204; and a gate electrode layer 127formed of the first gate electrode layer 124 and the second gateelectrode layer 134, a gate electrode layer 128 formed of the first gateelectrode layer 125 and the second gate electrode layer 135, and a gateelectrode layer 129 formed of the first gate electrode layer 126 and thesecond gate electrode layer 136 can be formed in a pixel region 206 (seeFIG. 2D). In this embodiment mode, the gate electrode layers are formedby dry etching; however, wet etching may also be employed.

The gate insulating layer 107 may be etched to some extent and reducedin thickness (so-called film decrease) by the etching step for formingthe gate electrode layers.

By forming a width of the gate electrode layer to be narrow, a thin filmtransistor capable of high speed operation can be formed. Two methodsfor forming a width of the gate electrode layer in a channel directionto be narrow will be described below.

A first method is to form a mask for a gate electrode layer and thenslim the mask in a width direction by etching, asking or the like toform a mask with a narrower width. By using the mask formed with anarrower width in advance, the gate electrode layer can also be formedin a shape with a narrower width.

A second method is to form a normal mask and then form a gate electrodelayer using the mask. Then, the obtained gate electrode layer isnarrowed in a width direction by conducting a side-etching. Accordingly,a gate electrode layer with a narrower width can be finally formed.Through the aforementioned steps, a thin film transistor with a shortchannel length can be formed, which can realize a thin film transistorcapable of high speed operation.

Next, an impurity element 151 which imparts n-type conductivity is addedusing the gate electrode layers 117, 118, 127, 128, and 129 as masks toform first n-type impurity regions 140 a, 140 b, 141 a, 141 b, 142 a,142 b, 142 c, 143 a, and 143 b (see FIG. 3A). In this embodiment mode,doping is performed by using phosphine (PH₃) as a doping gas containingan impurity element (in the doping gas, PH₃ is diluted with hydrogen(H₂), and the ratio of PH₃ in the gas is 5%) with a gas flow rate of 80sccm, a beam current of 54 μA/cm, an acceleration voltage of 50 kV, anda dose amount of 7.0×10¹³ ions/cm². Here, doping is performed so thatthe impurity element which imparts n-type conductivity is contained in aconcentration of about 1×10¹⁷ to 5×10¹⁸/cm³ in the first n-type impurityregions 140 a, 140 b, 141 a, 141 b, 142 a, 142 b, 142 c, 143 a, and 143h. In this embodiment mode, phosphorus (P) is used as the impurityelement which imparts n-type conductivity.

In this embodiment mode, regions of the impurity regions, which overlapwith the gate electrode layers with the gate insulating layer interposedtherebetween, are denoted as Lov regions. Further, regions of theimpurity regions, which do not overlap with the gate electrode layerswith the gate insulating layer interposed therebetween, are denoted asLoff regions. In FIGS. 3A to 3C, these regions are shown by hatching andblank spaces in the impurity regions. This does not mean that the blankspaces are not doped with impurity elements, but makes it easy tounderstand that the concentration distribution of the impurity elementin these regions reflects the mask and the doping condition. It is to benoted that this is the same in other drawings of this specification.

Subsequently, as shown in FIG. 3B, masks 153 a, 153 b, 153 c, and 153 dwhich cover the semiconductor layer 103, a part of the semiconductorlayer 105, and the semiconductor layer 106 are formed. By using themasks 153 a, 153 b, 153 c, and 153 d, and the second gate electrodelayer 132 as masks, an impurity element 152 which imparts n-typeconductivity is added to form second n-type impurity regions 144 a and144 b, third n-type impurity regions 145 a and 145 b, second n-typeimpurity regions 147 a, 147 b and 147 c, third n-type impurity regions148 a, 148 b, 148 c, and 148 d. In this embodiment mode, doping isperformed by using PH₃ as a doping gas containing an impurity element(in the doping gas, PH₃ is diluted with hydrogen (H₂), and the ratio ofPH₃ in the gas is 5%) with a gas flow rate of 80 sccm, a beam current of540 μA/cm, an acceleration voltage of 70 kV, and a dose amount of5.0×10¹⁵ ions/cm². Here, doping is performed so that each of the secondn-type impurity regions 144 a and 144 b contains the impurity elementwhich imparts n-type conductivity in a concentration of about 5×10¹⁹ to5×10²⁰/cm³. The third n-type impurity regions 145 a and 145 b are formedto contain the impurity element which imparts n-type conductivity inalmost the same concentration as the third n-type impurity regions 148a, 148 b, 148 c, and 148 d, or a little higher concentration. Further, achannel formation region 146 is formed in the semiconductor layer 104,and channel formation regions 149 a and 149 b are formed in thesemiconductor layer 105.

The second n-type impurity regions 144 a, 144 b, 147 a, 147 b, and 147 care high concentration n-type impurity regions which function as sourcesand drains. On the other hand, the third n-type impurity regions 145 a,145 b, 148 a, 148 b, 148 c, and 148 d are low concentration impurityregions which function as LDD (Lightly Doped Drain) regions. The n-typeimpurity regions 145 a and 145 b overlapped with the first gateelectrode layer 122 with the gate insulating layer 107 interposedtherebetween are Lov regions which can relieve an electric field arounda drain and suppress deterioration of an on current due to hot carriers.As a result, a thin film transistor capable of high speed operation canbe formed. On the other hand, the third n-type impurity regions 148 a,148 b, 148 c, and 148 d are formed in Loff regions which are notoverlapped with the gate electrode layers 127 and 128, and can relievean electric field around a drain and suppress deterioration due to hotcarrier injection as well as reduce an off current. As a result, asemiconductor device with high reliability and low power consumption canbe manufactured.

Subsequently, as shown in FIG. 3C, the masks 153 a, 153 b, 153 c, and153 d are removed, and masks 155 a and 155 b which cover thesemiconductor layers 104 and 105 are formed. An impurity element 154which imparts p-type conductivity is added using the masks 155 a and 155b, the gate electrode layers 117 and 129 as masks to form first p-typeimpurity regions 160 a, 160 b, 163 a and 163 b, and second p-typeimpurity regions 161 a, 161 b, 164 a, and 164 b. In this embodimentmode, boron (B) is used as an impurity element, and doping is performedusing diborane (B₂H₆) as a doping gas containing an impurity element (inthe doping gas, B₂H₆ is diluted with hydrogen (H₂), and the ratio ofB₂H₆ in the gas is 15%) with a gas flow rate of 70 sccm, a beam currentof 180 μA/cm, an acceleration voltage of 80 kV, and a dose amount of2.0×10¹⁵ ions/cm². Here, doping is performed so that the first p-typeimpurity regions 160 a, 160 b, 163 a and 163 b and the second p-typeimpurity regions 161 a, 161 b, 164 a, and 164 b contain the impurityelement which imparts p-type conductivity in a concentration of about1×10²⁰ to 5×10²¹/cm³. In this embodiment mode, the second p-typeimpurity regions 161 a, 161 b, 164 a, and 164 b are formed in aself-alignment manner by reflecting the shapes of the gate electrodelayers 117 and 129 to contain the impurity element in a lowerconcentration than that of the first p-type impurity regions 160 a, 160b, 163 a, and 163 b. Further, a channel formation region 162 is formedin the semiconductor layer 103 and a channel formation region 165 isformed in the semiconductor layer 106.

The first p-type impurity regions 160 a, 160 b, 163 a, and 163 b arehigh concentration p-type impurity regions and serve as sources anddrains. On the other hand, the second p-type impurity regions 161 a, 161b, 164 a, and 164 b are low concentration impurity regions whichfunction as LDD (Lightly Doped Drain) regions. The second p-typeimpurity regions 161 a, 161 b, 164 a, and 164 b overlapped with thefirst gate electrode layers 121 and 126 with the gate insulating layer107 interposed therebetween are Lov regions which can relieve anelectric field around a drain and suppress deterioration of an oncurrent due to hot carriers.

The masks 155 a and 155 b are removed by O₂ ashing or using a resiststripping solution, and the oxide film is also removed. After that, aninsulating film, namely, a so-called sidewall may be formed so as tocover side surfaces of the gate electrode layers. The sidewall can beformed of an insulating film containing silicon by a plasma CVD methodor a low pressure CVD (LPCVD) method.

In order to activate the impurity element, heat treatment, strong lightirradiation, or laser light irradiation may be performed. At the sametime as the activation, plasma damage to the gate insulating layer andplasma damage to an interface between the gate insulating layer and thesemiconductor layer can be recovered.

Subsequently, an interlayer insulating layer which covers the gateelectrode layers and the gate insulating layer is formed. In thisembodiment mode, a stacked-layer structure of insulating films 167 and168 is employed (see FIG. 4A). A silicon nitride oxide film is formed asthe insulating film 167 to be 100 nm thick, and a silicon oxynitridefilm is formed as the insulating film 168 to be 900 nm thick to form astacked-layer structure. Further, a stacked-layer structure of threelayers may be employed by forming a silicon oxynitride film to be 30 nmthick, a silicon nitride oxide film to be 140 nm thick, and a siliconoxynitride film to be 800 nm thick to cover the gate electrode layersand the gate insulating layer. In this embodiment mode, the insulatingfilms 167 and 168 are continuously formed by a plasma CVD methodsimilarly to the base film. The insulating films 167 and 168 are notlimited to the above materials and may be formed by using a siliconnitride film, a silicon nitride oxide film, a silicon oxynitride film,or a silicon oxide film by a sputtering method or a plasma CVD method.Alternatively, a single layer structure or a stacked-layer structure ofthree or more layers of other insulating film containing silicon mayalso be employed.

Further, heat treatment is performed in a nitrogen atmosphere at 300 to550° C. for 1 to 12 hours, and the semiconductor layer is hydrogenated.Preferably, this step is performed at 400 to 500° C. Through this step,dangling bonds in the semiconductor layer are terminated by hydrogencontained in the insulating film 167 that is an interlayer insulatinglayer. In this embodiment mode, heat treatment is performed at 410° C.for one hour.

In addition, the insulating films 167 and 168 can also be formed of amaterial selected from aluminum nitride (MN), aluminum oxynitride(AlON), aluminum nitride oxide containing more nitrogen than oxygen(AlNO), aluminum oxide, diamond-like carbon (DLC), a nitrogen-containingcarbon film (CN), and other substance containing an inorganic insulatingmaterial. A siloxane resin may also be used. The siloxane resin is aresin including a Si—O—Si bond. Siloxane has a skeleton structure formedof a bond of silicon (Si) and oxygen (O). As a substituent, an organicgroup containing at least hydrogen (for example, an alkyl group oraromatic hydrocarbon) or a fluoro group may be used. In addition, as asubstituent, both of an organic group containing at least hydrogen and afluoro group may also be used. Further, an organic insulating materialsuch as polyimide, acrylic, polyamide, polyimide amide, resist,benzocyclobutene, or polysilazane may also be used. A coated film with afavorable planarity formed by a coating method may also be used.

Subsequently, contact holes (openings), which reach the semiconductorlayers, are formed in the insulating films 167 and 168, and the gateinsulating layer 107 using a mask made of a resist. Etching may beperformed once or plural times in accordance with a selection ratio of amaterial to be used. In this embodiment mode, a first etching isperformed to remove the insulating film 168 with a condition where aselection ratio of the insulating film 168 that is a silicon oxynitridefilm to the insulating film 167 that is a silicon nitride oxide film andthe gate insulating layer 107 is high. Then, the insulating film 167 andthe gate insulating layer 107 are removed by second etching to formopenings, which reach the first p-type impurity regions 160 a, 160 b,163 a and 163 b and the second n-type impurity regions 144 a, 144 b, 147a and 147 b as source regions or drain regions. In this embodiment mode,the first etching is performed by wet etching whereas the second etchingis performed by dry etching. A hydrofluoric acid-based solution such asa mixed solution of ammonium hydrogen fluoride and ammonium fluoride maybe used as an etchant of wet etching. As an etching gas, CHF₃, C₂F₆,C₂F₈, C₄F₈, C₅F₈ or the like can be appropriately used, in addition to achlorine based gas typified by Cl₂, BCl₃, SiCl₄, CCl₄, or the like, afluorine based gas typified by CF₄, SF₆, NF₃, or the like, or O₂.Further, an inert gas may be added to an etching gas to be used. As aninert element to be added, one or a plurality of elements selected fromHe, Ne, Ar, Kr, and Xe can be used.

A conductive film is formed so as to cover the openings, and theconductive film is etched to form source electrode layers or drainelectrode layers 169 a, 169 b, 170 a, 170 b, 171 a, 171 b, 172 a, and172 b, each of which is electrically connected to a part of each sourceregion or drain region. The source electrode layer or the drainelectrode layer can be formed by forming a conductive film by a PVDmethod, a CVD method, an evaporation method, or the like, and then,etching the conductive film into a desired shape. Further, a conductivefilm can be selectively formed in a predetermined position by adroplet-discharge method, a printing method, an electroplating method,or the like. Moreover, a reflow method or a damascene method may also beused. As a material for the source electrode layer or the drainelectrode layer, a metal such as Ag, Au, Cu, Ni, Pt, Pd, Ir, Rh, W, Al,Ta, Mo, Cd, Zn, Fe, Ti, Zr, or Ba, or Si or Ge, an alloy or nitridethereof can be used. A stacked structure of these materials may also beemployed. In this embodiment mode, titanium (Ti) is formed to be 60 nmthick, a titanium nitride film is formed to be 40 nm thick, aluminum isformed to be 700 nm thick, and titanium (Ti) is formed to be 200 nmthick, and then, the stacked film is processed into a desired shape.

Through the above steps, an active matrix substrate can be manufactured,in which a p-channel thin film transistor 173 having a p-type impurityregion in a Lov region and an n-channel thin film transistor 174 havingan n-type impurity region in a Lov region are provided in the peripheraldriver circuit region 204; and a multi-channel type n-channel thin filmtransistor 175 having an n-type impurity region in a Loff region and ap-channel thin film transistor 176 having a p-type impurity region in aLov region are provided in the pixel region 206 (see FIG. 4B).

The active matrix substrate can be used for a light-emitting devicehaving a light-emitting element, a liquid crystal display device havinga liquid crystal, and other display devices.

A structure of the thin film transistor in the pixel portion is notlimited to this embodiment mode, and a single gate structure in whichone channel formation region is formed, a double gate structure in whichtwo channel formation regions are formed, or a triple gate structure inwhich three channel formation regions are formed may be employed.Further, the thin film transistor in the peripheral driver circuitregion may also employ a single gate structure, a double gate structure,or a triple gate structure.

The present invention is not limited to be applied to a manufacturingmethod of the thin film transistor shown in this embodiment mode, and itmay also be applied to a top gate type (a planar type), a bottom gatetype (a reverse staggered type), or a dual gate type having two gateelectrode layers which are arranged above and below a channel regionwith a gate insulating film interposed therebetween, or other structure.

Next, an insulating layer 181 is formed as a second interlayerinsulating layer (see FIG. 5A). FIGS. 5A to 5C each show a manufacturingstep of the display device, in which a separation region 201 forseparation by scribing, an external terminal connection region 202 thatis a portion where an FPC is attached, a wiring region 203 that is alead wiring region for the peripheral region, the peripheral drivercircuit region 204, and the pixel region 206 are provided. Wirings 179 aand 179 b are provided in the wiring region 203, and a terminalelectrode layer 178 connected to an external terminal is provided in theexternal terminal connection region 202.

The insulating layer 181 can be formed by using a material selected fromsilicon oxide, silicone nitride, silicon oxynitride, silicon nitrideoxide, aluminum nitride (AlN), aluminum oxynitride (AlON), aluminumnitride oxide (AlNO) containing more nitrogen than oxygen, aluminiumoxide, diamond like carbon (DLC), nitrogen-containing carbon (CN) film,PSG (phosphorus glass), BPSG (boron phosphorus glass), an alumina film,and other substance containing an inorganic insulating material. Inaddition, a siloxane resin may also be used. Further, a photosensitiveor non-photosensitive organic insulating material such as polyimide,acrylic, polyamide, polyimide amide, resist, benzocyclobutene,polysilazane, or a Low-k material having a low dielectric constant mayalso be used.

In this embodiment mode, the interlayer insulating layer provided forplanarization is required to have a high heat resistant property, a highinsulating property, and high planarity. Thus, the insulating layer 181is preferably formed by using a coating method typified by a spincoating method.

In this embodiment mode, as a material for the insulating layer 181, acoated film using a siloxane resin is used. The siloxane resin filmafter baking can resist heat treatment at 300° C. or higher.

The insulating layer 181 can be formed by using dipping, spray coating,a doctor knife, a roll coater, a curtain coater, a knife coater, a CVDmethod, an evaporation method, or the like. The insulating layer 181 mayalso be formed by a droplet-discharge method. In a case of using adroplet-discharge method, a material solution can be saved. In addition,a method capable of transferring or describing a pattern similarly to adroplet-discharge method, for example, a printing method (a method offorming a pattern such as screen printing or offset printing) can alsobe used.

Then, as shown in FIGS. 5B and 5C, an opening is formed in theinsulating layer 181 that is the second interlayer insulating layer. Theinsulating layer 181 is required to be etched widely in a connectionregion (not shown in the drawing), the wiring region 203, the externalterminal connection region 202, the separation region 201, and the like.However, in the pixel region 206, an opening area is much smallercompared with an opening area in the connection region and the like, andis minute. Therefore, by carrying out both of a photolithography stepfor forming the opening in the pixel region and a photolithography stepfor forming the opening in the connection region and the like, a marginof an etching condition can be wide. As a result, yield can be improved.Further, by a wide margin of the etching condition, the contact holeformed in the pixel region can be formed with high precision.

Specifically, a large area opening is formed in the insulating layer 181provided in the connection region, the wiring region 203, the externalterminal connection region 202, the separation region 201, and theperipheral driver circuit region 204. Therefore, a mask is formed tocover at least the insulating layer 181 in the pixel region 206. Etchingcan be performed by using a parallel plate RIE apparatus or an ICPetching apparatus. It is to be noted that etching time may be determinedso that the wiring layer and the first interlayer insulating layer areover-etched. Under the condition where the wiring layer and the firstinterlayer insulating layer are over-etched, variation in thickness inthe substrate and variation in etching rate can be reduced. In thismanner, an opening 183 is formed in the external terminal connectionregion 202.

Thereafter, a minute opening, that is, a contact hole is formed in theinsulating layer 181 in the pixel region 206 (see FIG. 5C). At thistime, a mask for forming an opening in the pixel region 206 providedwith a minute opening in a predetermined position is formed. As such amask, for example, a resist mask can be used.

Then, the insulating layer 181 is etched by using a parallel plate RIEapparatus. It is to be noted that etching time may be determined so thatthe wiring layer and the first interlayer insulating layer areover-etched. Under the condition where the wiring layer and the firstinterlayer insulating layer are over-etched, variation in thickness inthe substrate and variation in etching rate can be reduced.

Further, an ICP apparatus may also be used as the etching apparatus.Through the above steps, an opening 184 that reaches the sourceelectrode layer or the drain electrode layer 172 a is formed in thepixel region 206. In addition, the source electrode layer or the drainelectrode layer connected to a first electrode layer can also be formedin a region in which many thin films are stacked and a total thicknessis thick. In the thin film transistor in this embodiment mode, thesource electrode layer or the drain electrode layer may be formed overthe gate electrode layer. In this case, the opening 184 is not requiredto be opened with a deep thickness, thereby an opening step can beshortened to improve controllability. Further, since an electrode layerformed in the opening is not required to widely cover an opening with alarge angle either, the electrode can be formed with excellent coverageand reliability can be improved.

In this embodiment mode, the case where the insulating layer 181 in thewiring region 203, the external terminal connection region 202, theseparation region 201, and the insulating layer 181 in the peripheraldriver circuit region 204 and the insulating layer 181 in the pixelregion 206 are each processed by performing one etching step; however,the present invention is not limited thereto. For example, since theopening of the connection region has a large area, an amount of etchingis large. Such an opening with a large area may be formed by performingetching plural times. Further, in the case of forming a deeper openingcompared with other opening, etching may be performed plural times,similarly.

Further, in this embodiment mode, although the openings are formed inthe insulating layer 181 by performing etchings separately plural timesas shown in FIGS. 5B and 5C, the openings may also be formed byperforming one etching step. In this case, etching is performed using anICP apparatus with an ICP power of 7000 W, a bias power of 1000 W,pressure of 0.8 Pascal (Pa), and 240 sccm of CF₄ and 160 sccm O₂ as anetching gas. The bias power is preferably 1000 to 4000 W. Since theopenings can be formed by one etching step, there is an advantage that astep can be simplified.

Subsequently, a first electrode layer 396 (also referred to as a pixelelectrode layer) is formed so as to be in contact with the sourceelectrode layer or the drain electrode layer 172 a or 172 b.

In this embodiment mode, a light-emitting element is used as a displayelement, and the first electrode layer 396 has a light-transmittingproperty because light from the light-emitting element is extracted fromthe first electrode layer 396 side. The first electrode layer 396 isformed by using a light-transmitting conductive material.

In the present invention, the first electrode layer 396 that is alight-transmitting electrode layer may be specifically formed by using atransparent conductive film formed of a light-transmitting conductivematerial, and indium oxide containing tungsten oxide, indium zinc oxidecontaining tungsten oxide (hereinafter also referred to as an IWZOfilm), indium oxide containing titanium oxide, indium tin oxidecontaining titanium oxide, and the like can be used. (FIG. 6A)

Further, silicon oxide may be added into indium oxide containingtungsten oxide, indium zinc oxide containing tungsten oxide, indiumoxide containing titanium oxide, and indium tin oxide containingtitanium oxide. In a sputtering method where a thin film is formed bysputtering a target, unevenness called a nodule is generated on a targetsurface to which sputtering is performed. When a target having an unevenshape is used, a film with uniform composition cannot be formed, a largelump of a material is generated like a dust in the film, and a densefilm cannot be obtained. When sputtering is performed by using a targetin which silicon oxide is added into a transparent conductive materialas described above, unevenness on the target surface can be reduced, anda uniform and dense film can be obtained. The ratio of the added siliconoxide is about 5 to 10 wt %.

An example of a composition ratio of each light-transmitting conductivematerial is described. In indium oxide containing tungsten oxide, thecomposition ratio of tungsten oxide may be 1.0 wt % and indium oxide maybe 99.0 wt %. In indium zinc oxide containing tungsten oxide, tungstenoxide may be 1.0 wt %, zinc oxide may be 0.5 wt %, and indium oxide maybe 98.5 wt %. In indium oxide containing titanium oxide, titanium oxidemay be 1.0 to 5.0 wt % and indium oxide may be 99.0 to 95.0 wt %. Inindium tin oxide (ITO), tin oxide may be 10.0 wt % and indium oxide maybe 90.0 wt %. In indium zinc oxide (IZO), zinc oxide may be 10.7 wt %and indium oxide may be 89.3 wt %. Further, in indium tin oxidecontaining titanium oxide, titanium oxide may be 5.0 wt %, tin oxide maybe 10.0 wt %, and indium oxide may be 85.0 wt %. The composition ratiosas described above are just examples, and a composition ratio may be setappropriately.

The first electrode layer 396 can be formed by an evaporation method, asputtering method, or the like. In a case of using a sputtering method,a gas containing water (water vapor (H₂O)) or H₂ may be used as a gas.In this embodiment mode, as the first electrode layer 396, an indiumzinc oxide film containing silicon oxide and tungsten oxide is formed byusing indium zinc oxide containing tungsten oxide into which siliconoxide is added as a target by a sputtering method using a gas containingwater (H₂O) or H₂. In this embodiment mode, silicon oxide is added intoindium zinc oxide containing tungsten oxide by 10 wt %. The firstelectrode layer 396 may be formed in a total thickness range of 100 to800 nm, and is 185 nm in this embodiment mode. In this embodiment mode,a gas containing 50 sccm of argon (Ar), 1.0 sccm of oxygen (O₂), and 0.2sccm of H₂ is used. The gas containing water (vapor water (H₂O)) used inthe present invention does not mean a gas containing water to someextent depending on a manufacturing method or a storage method, but agas containing water as one of the main components. In case of using anH₂O gas, the flow rate is preferably 0.5 sccm or less. The indium zincoxide film containing silicon oxide and tungsten oxide formed in thisembodiment mode has favorable processability, and can be etched withoutleaving a residue by wet etching using weak acid. When such a film isused for a pixel electrode of a display device, a highly reliabledisplay device can be manufactured, in which light extraction efficiencyof a light-emitting element is favorable, and defects due to an etchingdefect of an electrode or the like are suppressed. In addition, thefirst electrode layer 396 functions as an etching stopper in etching toform an insulating layer 186 functioning as a partition wall.

The surface of the first electrode layer 396 may be polished by a CMPmethod or by cleaning with a poly(vinyl alcohol) based porous body to beplanarized. After polishing by a CMP method, ultraviolet rayirradiation, oxygen plasma treatment, or the like may be performed tothe surface of the first electrode layer 396 so that the surface isreformed.

Heat treatment may be performed after forming the first electrode layer396. By the heat treatment, moisture contained in the first electrodelayer 396 is discharged. Accordingly, degasification or the like is notcaused in the first electrode layer 396. Thus, even when alight-emitting material which is easily deteriorated by moisture isformed over the first electrode layer, the light-emitting material isnot deteriorated; therefore, a highly reliable display device can bemanufactured. In this embodiment mode, light is emitted by flowing acurrent through a layer containing an organic compound used as anelectroluminescent layer, and thus, the layer is required to be thin tosome extent. In this embodiment mode, the indium zinc oxide filmcontaining silicon oxide and tungsten oxide is used for the firstelectrode layer 396 so that it is hardly crystallized even when bakingis performed, and an amorphous state is kept. Hence, the first electrodelayer 396 has high planarity, and short-circuit with a second electrodelayer is hardly caused even when the layer containing an organiccompound is thin.

In this embodiment mode, photosensitive polyimide is used for theinsulating layer 186. When the insulating layer 186 is formed by usingthe same material and through the same step as the insulating layer 181,a manufacturing cost can be reduced. In addition, the cost can also bereduced when apparatuses such as a coating film forming apparatus and anetching apparatus can be used in common. (FIG. 6B)

The insulating layer 186 can be formed by using silicon oxide, siliconnitride, silicon oxynitride, aluminum oxide, aluminum nitride, aluminumoxynitride, or other inorganic insulating material; acrylic acid,methacrylic acid, or a derivative thereof; a heat-resistanthigh-molecular material such as polyimide, aromatic polyamide, orpolybenzimidazole; or an insulating material such as a siloxane resin.Alternatively, the insulating layer 186 may be formed by using aphotosensitive or non-photosensitive material such as acrylic orpolyimide. The insulating layer 186 preferably has a shape where aradius of curvature continuously changes. Accordingly, coverage of anelectroluminescent layer 188 and a second electrode layer 189 which areformed thereover is improved.

In a connection region 205 shown in FIG. 1A, a wiring layer formed bythe same material and through the same step as the second electrodelayer is electrically connected to a wiring layer formed by the samematerial and through the same step as the gate electrode layer. For thisconnection, an opening is formed to expose the wiring layer formed bythe same material and through the same step as the gate electrode layer.A step around the opening is covered with the insulating layer 186 to bea gentle sloping, and thus, the coverage of the second electrode layer189 to be stacked thereover can be improved.

Further, in order to further improve reliability, it is preferable toperform degasification of the substrate by vacuum heating before formingthe electroluminescent layer 188. For example, before performingevaporation of an organic compound material, it is desirable to performheat treatment for removing a gas contained in the substrate in areduced pressure atmosphere or an inert gas atmosphere at 200 to 400°C., preferably 250 to 350° C. Further, it is preferable to form theelectroluminescent layer 188 by a vacuum evaporation method or adroplet-discharge method under a reduced pressure without exposing thesubstrate to atmospheric air. By this heat treatment, moisture containedin or attached to a conductive film to be the first electrode layer oran insulating layer (partition wall) can be discharged. This heattreatment can be combined with a prior heating step as long as thesubstrate can be transferred in a vacuum chamber without breaking thevacuum, and only the prior heat treatment may be required to beperformed once after forming an insulating layer (partition wall). Here,by forming the interlayer insulating film and the insulating layer(partition wall) using a highly heat resistant substance, a heattreatment step for improving the reliability can be sufficiently carriedout.

The electroluminescent layer 188 is formed over the first electrodelayer 396. Although only one pixel is shown in FIG. 1B, anelectroluminescent layer corresponding to each color of R (red), G(green) and B (blue) is separately formed in this embodiment mode. Theelectroluminescent layer 188 may be manufactured as will be describedlater. By mixing an organic compound and an inorganic compound, layershaving functions of a high carrier injecting property and a high carriertransporting property, which cannot be obtained when only one of anorganic compound and an inorganic compound is used, are provided overthe first electrode layer 396.

Materials (a low-molecular material, a high-molecular material, or thelike), which show light-emission of red (R), green (G), and blue (B),can also be formed by a droplet-discharge method.

Subsequently, the second electrode layer 189 formed of a conductive filmis provided over the electroluminescent layer 188. As the secondelectrode layer 189, a material having a low work function (In, Al, Ag,Li, Ca, or an alloy containing these metals such as MgAg, MgIn, AlLi, orCaF₂ or calcium nitride) may be used. In this manner, a light-emittingelement 190 formed of the first electrode layer 396, theelectroluminescent layer 188, and the second electrode layer 189 isformed.

A structure of the light-emitting element 190 which can be employed inthis embodiment mode will be described in detail with reference to FIGS.18A to 18D. In FIGS. 18A to 18D, a first electrode layer 870 correspondsto the first electrode layer 396 in FIG. 1B, an electroluminescent layer860 corresponds to the electroluminescent layer 188, and a secondelectrode layer 850 corresponds to the second electrode layer 189.

FIGS. 18A to 18D show an element structure of the light-emittingelement, in which the electroluminescent layer 860 formed by mixing anorganic compound and an inorganic compound is interposed between thefirst electrode layer 870 and the second electrode layer 850. As shownin the drawings, the electroluminescent layer 860 is formed of a firstlayer 804, a second layer 803, and a third layer 802, and in particular,the first layer 804 and the third layer 802 have remarkable features.

The first layer 804 is a layer which has a function of transportingholes to the second layer 803, and includes at least a first organiccompound and a first inorganic compound having an electron-acceptingproperty with respect to the first organic compound. What is importantis that the first organic compound and the first inorganic compound arenot only simply mixed, but the first inorganic compound has anelectron-accepting property with respect to the first organic compound.This structure generates a lot of hole-carriers in the first organiccompound, which originally has almost no inherent carriers, and a highlyexcellent hole-injecting property and hole-transporting property can beobtained.

Therefore, as for the first layer 804, not only advantageous effect thatis considered to be obtained by mixing an inorganic compound (such asimprovement in a heat resistant property) but also excellentconductivity (in particular, a hole-injecting property and ahole-transporting property in the first layer 804) can be obtained. Thisexcellent conductivity is advantageous effect that cannot be obtained ina conventional hole-transporting layer in which an organic compound andan inorganic compound that do not electronically interact with eachother are simply mixed. This advantageous effect can make a drivevoltage lower than conventionally. In addition, since the first layer804 can be made thicker without causing increase in a drive voltage,short circuit of the element due to a dust and the like can besuppressed.

It is preferable to use a hole-transporting organic compound as thefirst organic compound since hole-carriers are generated in the firstorganic compound as described above. Examples of the hole-transportingorganic compound include, but are not limited to, phthalocyanine(abbreviation: H₂Pc), copper phthalocyanine (abbreviation: CuPc),vanadyl phthalocyanine (abbreviation: VOPc),4,4′,4″-tris(N,N-diphenylamino)triphenylamine (abbreviation: TDATA),4,4′,4″-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine(abbreviation: MTDATA), 1,3,5-tris[N,N-di(m-tolyl)amino]benzene(abbreviation: m-MTDAB),N,N′-diphenyl-N,N-bis(3-methylphenyl)-1,1′-biphenyl-4,4′-diamine(abbreviation: TPD), 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl(abbreviation: NPB),4,4′-bis{N-[4-di(m-tolyl)amino]phenyl-N-phenylamino}biphenyl(abbreviation: DNTPD), 4,4′,4″-tris(N-carbazolyl)triphenylamine(abbreviation: TCTA), and the like. In addition, among the compoundsmentioned above, aromatic amine compounds as typified by TDATA, MTDATA,m-MTDAB, TPD, NPB, DNTPD, and TCATA can easily generate hole-carriers,and are a suitable group of compounds for the first organic compound.

On the other hand, the first inorganic compound may be any material aslong as the material can easily accept electrons from the first organiccompound, and various kinds of metal oxide and metal nitride can beused. Transition metal oxide having a transition metal that belongs toany of Groups 4 to 12 of the periodic table is preferable since anelectron-accepting property is easily provided. Specifically, titaniumoxide, zirconium oxide, vanadium oxide, molybdenum oxide, tungstenoxide, rhenium oxide, ruthenium oxide, zinc oxide, and the like can beused. In addition, of the metal oxide mentioned above, many kinds oftransition metal oxide having a transition metal that belongs to any ofGroups 4 to 8 have a higher electron-accepting property, which arepreferable groups of compounds. In particular, vanadium oxide,molybdenum oxide, tungsten oxide, and rhenium oxide are preferable sincethey can be formed by vacuum evaporation and can be easily used.

It is to be noted that the first layer 804 may be formed by stacking aplurality of layers each including a combination of the organic compoundand the inorganic compound as described above, or may further includeanother organic compound or inorganic compound.

Next, the third layer 802 will be described. The third layer 802 is alayer which has a function of transporting electrons to the second layer803, and includes at least a third organic compound and a thirdinorganic compound having an electron-donating property with respect tothe third organic compound. What is important is that the third organiccompound and the third inorganic compound are not only simply mixed butalso the third inorganic compound has an electron-donating property withrespect to the third organic compound. This structure generates a lot ofelectron-carriers in the third organic compound which has originallyalmost no inherent carriers, and a highly excellent electron-injectingand electron-transporting property can be obtained.

Therefore, as for the third layer 802, not only advantageous effect thatis considered to be obtained by mixing an inorganic compound (such asimprovement in a heat resistant property) but also excellentconductivity (in particular, an electron-injecting property and anelectron-transporting property in the third layer 802) can also beobtained. This excellent conductivity is advantageous effect that cannotbe obtained in a conventional electron-transporting layer in which anorganic compound and an inorganic compound that do not electronicallyinteract with each other are simply mixed. This advantageous effect canmake a drive voltage lower than conventionally. In addition, since thethird layer 802 can be made thick without causing increase in a drivevoltage, short circuit of the element due to a dust and the like can besuppressed.

It is preferable to use an electron-transporting organic compound as thethird organic compound since electron-carriers are generated in thethird organic compound as described above. Examples of theelectron-transporting organic compound include, but are not limited to,tris(8-quinolinolato)aluminum (abbreviation: Alq₃),tris(4-methyl-8-quinolinolato)aluminum (abbreviation: Almq₃),bis(10-hydroxybenzo[h]-quinolinato)beryllium (abbreviation: BeBq₂),bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum (abbreviation:BAlq), bis[2-(2′-hydroxyphenyl)benzoxazolato]zinc (abbreviation:Zn(BOX)₂), bis[2-(2′-hydroxyphenyl)benzothiazolato]zinc (abbreviation:Zn(BTZ)₂), bathophenanthroline (abbreviation: BPhen), bathocuproin(abbreviation: BCP),2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation:PBD), 1,3-bis[5-(4-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene(abbreviation: OXD-7),2,2′,2″-(1,3,5-benzenetriyl)-tris(1-phenyl-1H-benzimidazole)(abbreviation: TPBI),3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole(abbreviation: TAZ),3-(4-biphenylyl)-4-(4-ethylphenyl)-5-(4-tert-butylphenyl)-1,2,4-triazole(abbreviation: p-EtTAZ), and the like. In addition, among the compoundsmentioned above, chelate metal complexes having a chelate ligandincluding an aromatic ring as typified by Alq₃, Almq₃, BeBq₂, BAlq,Zn(BOX)₂, and Zn(BTZ)₂, organic compounds having a phenanthrolineskeleton as typified by BPhen and BCP, and organic compounds having anoxadiazole skeleton as typified by PBD and OXD-7 can easily generateelectron-carriers, and are suitable groups of compounds for the thirdorganic compound.

On the other hand, the third inorganic compound may be any material aslong as the material can easily donate electrons to the third organiccompound, and various kinds of metal oxide and metal nitride can beused. Alkali metal oxide, alkaline-earth metal oxide, rare-earth metaloxide, alkali metal nitride, alkaline-earth metal nitride, andrare-earth metal nitride are preferable since an electron-donatingproperty is easily provided. Specifically, lithium oxide, strontiumoxide, barium oxide, erbium oxide, lithium nitride, magnesium nitride,calcium nitride, yttrium nitride, lanthanum nitride, and the like can beused. In particular, lithium oxide, barium oxide, lithium nitride,magnesium nitride, and calcium nitride are preferable since they can beformed by vacuum evaporation and can be easily used.

It is to be noted that the third layer 802 may be formed by stacking aplurality of layers each including a combination of the organic compoundand the inorganic compound as described above, or may further includeanother organic compound or inorganic compound.

Next, the second layer 803 will be described. The second layer 803 is alayer which has a function of emitting light, and includes a secondorganic compound that has a light-emitting property. A second inorganiccompound may also be included. The second layer 803 can be formed byusing various light-emitting organic compounds and inorganic compounds.However, since it is believed to be hard to flow a current through thesecond layer 803 as compared with the first layer 804 or the third layer802, the thickness of the second layer 803 is preferably about 10 to 100nm.

The second organic compound is not particularly limited as long as it isa light-emitting organic compound, and examples of the second organiccompound include, for example, 9,10-di(2-naphthyl)anthracene(abbreviation: DNA), 9,10-di(2-naphthyl)-2-tert-butylanthracene(abbreviation: t-BuDNA), 4,4′-bis(2,2-diphenylvinyl)biphenyl(abbreviation: DPVBi), coumarin 30, coumarin 6, coumarin 545, coumarin545T, perylene, rubrene, periflanthene,2,5,8,11-tetra(tert-butyl)perylene (abbreviation: TBP),9,10-diphenylanthracene (abbreviation: DPA), 5,12-diphenyltetracene,4-(dicyanomethylene)-2-methyl-[p-(dimethylamino)styryl]-4H-pyran(abbreviation: DCM1),4-(dicyanomethylene)-2-methyl-6-[2-(julolidine-9-yl)ethenyl]-4H-pyran(abbreviation: DCM2),4-(dicyanomethylene)-2,6-bis[p-(dimethylamino)styryl]-4H-pyran(abbreviation: BisDCM), and the like. In addition, it is also possibleto use a compound capable of emitting phosphorescence such asbis[2-(4′,6′-difluorophenyl)pyridinato-N,C^(2′)]iridium(picolinate)(abbreviation: FIrpic), bis{2-[3′,5′-bis(trifluoromethyl)phenyl]pyridinato-N,C^(2′)}iridium(picolinate)(abbreviation: Ir(CF₃ppy)₂(pic)),tris(2-phenylpyridinato-N,C^(2′))iridium (abbreviation: Ir(ppy)₃),bis(2-phenylpyridinato-N,C^(2′))iridium(acetylacetonate) (abbreviation:Ir(ppy)₂(acac)),bis[2-(2′-thienyl)pyridinato-N,C^(3′)]iridium(acetylacetonate)(abbreviation: Ir(thp)₂(acac)),bis(2-phenylquinolinato-N,C^(2′))iridium(acetylacetonate) (abbreviation:Ir(pq)₂(acac)), orbis[2-(2′-benzothienyl)pyridinato-N,C^(3′)]iridium(acetylacetonate)(abbreviation: Ir(btp)₂(acac)).

Further, a triplet excitation light-emitting material containing a metalcomplex or the like may be used for the second layer 803 in addition toa singlet excitation light-emitting material. For example, among pixelsemitting red, green, and blue light, a pixel emitting red light whoseluminance is reduced by half in a relatively short time is formed byusing a triplet excitation light-emitting material and the other pixelsare formed by using a singlet excitation light-emitting material. Atriplet excitation light-emitting material has a feature of favorablelight-emitting efficiency and less power consumption to obtain the sameluminance. In other words, when a triplet excitation light-emittingmaterial is used for a red pixel, only small amount of current needs tobe applied to a light-emitting element, and thus, reliability can beimproved. A pixel emitting red light and a pixel emitting green lightmay be formed by using a triplet excitation light-emitting material anda pixel emitting blue light may be formed by using a singlet excitationlight-emitting material to achieve low power consumption as well. Lowpower consumption can be further achieved by forming a light-emittingelement emitting green light that has high visibility for human eyes byusing a triplet excitation light-emitting material.

The second layer 803 may include not only the second organic compound asdescribed above, which produces light-emission, but also another organiccompound may also be added thereto. Examples of organic compounds thatcan be added include, but are not limited to, TDATA, MTDATA, m-MTDAB,TPD, NPB, DNTPD, TCTA, Alq₃, Almq₃, BeBq₂, BAlq, Zn(BOX)₂, Zn(BTZ)₂,BPhen, BCP, PBD, OXD-7, TPBI, TAZ, p-EtTAZ, DNA, t-BuDNA, and DPVBi,which are mentioned above, and further, 4,4′-bis(N-carbazolyl)biphenyl(abbreviation: CBP), 1,3,5-tris[4-(N-carbazolyl)phenyl]benzene(abbreviation: TCPB), and the like. It is preferable that the organiccompound, which is added in addition to the second organic compound,have larger excitation energy than that of the second organic compoundand be added by the larger amount than the second organic compound inorder to make the second organic compound emit light efficiently (whichmakes it possible to prevent concentration quenching of the secondorganic compound). Alternatively, as another function, the added organiccompound may emit light along with the second organic compound (whichmakes it possible to emit white light and the like).

The second layer 803 may have a structure to perform color display byproviding each pixel with a light-emitting layer having a differentemission wavelength range. Typically, a light-emitting layercorresponding to each color of R (red), G (green), and B (blue) isformed. Also in this case, color purity can be improved and a pixelportion can be prevented from having a mirror surface (reflection) byproviding the light-emission side of the pixel with a filter whichtransmits light of an emission wavelength range of the light. Byproviding a filter, a circularly polarizing plate or the like that hasbeen conventionally required can be omitted, and further, the loss oflight emitted from the light-emitting layer can be eliminated. Moreover,change in a color tone, which occurs when a pixel portion (displayscreen) is obliquely seen, can be reduced.

Either a high-molecular organic light-emitting material or alow-molecular organic light-emitting material can be used for a materialof the second layer 803. A high-molecular organic light-emittingmaterial is physically stronger as compared with a low-molecularmaterial and is superior in durability of the element. In addition, ahigh-molecular organic light-emitting material can be formed by coating;therefore, the element can be relatively easily manufactured.

The emission color is determined depending on a material forming thelight-emitting layer; therefore, a light-emitting element which exhibitsdesired light-emission can be formed by selecting an appropriatematerial for the light-emitting layer. As a high-molecularelectroluminescent material which can be used for forming alight-emitting layer, a polyparaphenylene-vinylene-based material, apolyparaphenylene-based material, a polythiophene-based material, or apolyfluorene-based material can be used.

As the polyparaphenylene-vinylene-based material, a derivative ofpoly(paraphenylenevinylene) [PPV] such aspoly(2,5-dialkoxy-1,4-phenylenevinylene) [RO-PPV];poly(2-(2′-ethyl-hexoxy)-5-methoxy-1,4-phenylenevinylene) [MEH-PPV]; orpoly(2-(dialkoxyphenyl)-1,4-phenylenevinylene) [ROPh-PPV] can be given.As the polyparaphenylene-based material, a derivative ofpolyparaphenylene [PPP] such as poly(2,5-dialkoxy-1,4-phenylene)[RO-PPP]; or poly(2,5-dihexoxy-1,4-phenylene) can be given. As thepolythiophene-based material, a derivative of polythiophene [PT] such aspoly(3-alkylthiophene) [PAT]; poly(3-hexylthiophen) [PHT];poly(3-cyclohexylthiophen) [PCHT]; poly(3-cyclohexyl-4-methylthiophene)[PCHMT]; poly(3,4-dicyclohexylthiophene) [PDCHT];poly[3-(4-octylphenyl)-thiophene] [POPT]; orpoly[3-(4-octylphenyl)-2,2bithiophene] [PTOPT] can be given. As thepolyfluorene-based material, a derivative of polyfluorene [PF] such aspoly(9,9-dialkylfluorene) [PDAF] or poly(9,9-dioctylfluorene) [PDOF] canbe given.

The second inorganic compound may be any inorganic compound as long aslight-emission of the second organic compound is not easily quenched bythe inorganic compound, and various kinds of metal oxide and metalnitride can be used. In particular, metal oxide having a metal thatbelongs to Group 13 or 14 of the periodic table is preferable sincelight-emission of the second organic compound is not easily quenched,and specifically, aluminum oxide, gallium oxide, silicon oxide, andgermanium oxide are preferable. However, the second inorganic compoundis not limited thereto.

It is to be noted that the second layer 803 may be formed by stacking aplurality of layers each including a combination of the organic compoundand the inorganic compound as described above, or may further includeanother organic compound or inorganic compound. A layer structure of thelight-emitting layer can be changed, and an electrode layer forinjecting electrons may be provided or a light-emitting material may bedispersed, instead of providing no specific electron-injecting region orlight-emitting region. Such a change can be permitted unless it departsfrom the spirit of the present invention.

A light-emitting element formed by using the above described materialsemits light by being forwardly biased. A pixel of a display device whichis formed by using a light-emitting element can be driven by a simplematrix (passive matrix) mode or an active matrix mode. In any case, eachpixel emits light by applying a forward bias thereto at a specifictiming; however, the pixel is in a non-emitting state for a certainperiod. Reliability of a light-emitting element can be improved byapplying a reverse bias in the non-emitting time. In a light-emittingelement, there is a deterioration mode in which emission intensity isdecreased under constant driving conditions or a deterioration mode inwhich a non-light-emitting region is enlarged in the pixel and luminanceis apparently decreased. However, progression of deterioration can beslowed down by alternating current driving where bias is appliedforwardly and reversely, and thus, reliability of a light-emittingdisplay device can be improved. Additionally, either digital driving oranalog driving can be applied.

A color filter (colored layer) may be formed on a sealing substrate. Thecolor filter (colored layer) can be formed by an evaporation method or adroplet-discharge method. With the use of the color filter (coloredlayer), high-definition display can be performed. This is because abroad peak can be modified to be sharp in an emission spectrum of eachof R, G, and B by the color filter (colored layer).

Full color display can be performed by forming a material emitting lightof a single color and combining with a color filter or a colorconversion layer. The color filter (colored layer) or the colorconversion layer may be formed over, for example, a second substrate (asealing substrate) and may be attached to a substrate.

Obviously, display of a single color emission may also be performed. Forexample, an area color type display device may be manufactured by usingsingle color emission. The area color type is suitable for a passivematrix display portion, and can mainly display characters and symbols.

Materials of the first electrode layer 870 and the second electrodelayer 850 are required to be selected considering the work function. Thefirst electrode layer 870 and the second electrode layer 850 can beeither an anode or a cathode depending on the pixel structure. In a casewhere polarity of a driving thin film transistor is a p-channel type,the first electrode layer 870 may serve as an anode and the secondelectrode layer 850 may serve as a cathode as shown in FIG. 18A. In acase where polarity of the driving thin film transistor is an n-channeltype, the first electrode layer 870 may serve as a cathode and thesecond electrode layer 850 may serve as an anode as shown in FIG. 18B.Materials that can be used for the first electrode layer 870 and thesecond electrode layer 850 will be described. It is preferable to use amaterial having a higher work function (specifically, a material havinga work function of 4.5 eV or higher) for one of the first electrodelayer 870 and the second electrode layer 850, which serve as an anode,and a material having a lower work function (specifically, a materialhaving a work function of 3.5 eV or lower) for the other electrode layerwhich serves as a cathode. However, since the first layer 804 issuperior in a hole-injecting property and a hole-transporting propertyand the third layer 802 is superior in an electron-injecting propertyand an electron transporting property, both of the first electrode layer870 and the second electrode layer 850 are scarcely restricted by a workfunction, and various materials can be used.

The light-emitting elements shown in FIGS. 18A and 18B have a structurein which light is extracted from the first electrode layer 870, andthus, the second electrode layer 850 is not always required to have alight-transmitting property. The second electrode layer 850 may beformed of a film mainly including an element selected from Ti, TiN,TiSi_(X)N_(Y), Ni, W, WSi_(X), WN_(X), WSi_(X)N_(Y), NbN, Cr, Pt, Zn,Sn, In, Ta, Al, Cu, Au, Ag, Mg, Ca, Li and Mo, or an alloy material or acompound material containing the element as its main component, or astacked film thereof in a total thickness range of 100 to 800 nm.

The second electrode layer 850 can be formed by an evaporation method, asputtering method, a CVD method, a printing method, a droplet-dischargemethod, or the like.

In addition, when the second electrode layer 850 is formed by using alight-transmitting conductive material similarly to the material usedfor the first electrode layer 870, light is also extracted from thesecond electrode layer 850, and a dual emission structure can beobtained, in which light emitted from the light-emitting element isemitted from both of the first electrode layer 870 side and the secondelectrode layer 850 side.

It is to be noted that the light-emitting element according to thepresent invention has variations by changing types of the firstelectrode layer 870 and the second electrode layer 850.

FIG. 18B shows a case where the third layer 802, the second layer 803,and the first layer 804 are provided in this order from the firstelectrode layer 870 side in the electroluminescent layer 860.

As described above, in the light-emitting element according to thepresent invention, the layer interposed between the first electrodelayer 870 and the second electrode layer 850 is formed of theelectroluminescent layer 860 including a layer in which an organiccompound and an inorganic compound are combined. The light-emittingelement is an organic-inorganic composite light-emitting elementprovided with layers (that is, the first layer 804 and the third layer802) that provide functions called a high carrier-injecting property andcarrier-transporting property by mixing an organic compound and aninorganic compound, where the functions are not obtainable from onlyeither one of the organic compound or the inorganic compound. Further,the first layer 804 and the third layer 802 are particularly required tobe layers in which an organic compound and an inorganic compound arecombined when provided on the first electrode layer 870 side, and maycontain only one of an organic compound and an inorganic compound whenprovided on the second electrode layer 850 side.

Further, various methods can be used as a method for forming theelectroluminescent layer 860, which is a layer in which an organiccompound and an inorganic compound are mixed. For example, the methodsinclude a co-evaporation method of evaporating both an organic compoundand an inorganic compound by resistance heating. In addition, forco-evaporation, an inorganic compound may be evaporated by an electronbeam (EB) while evaporating an organic compound by resistance heating.Further, the methods also include a method of sputtering an inorganiccompound while evaporating an organic compound by resistance heating todeposit the both at the same time. In addition, the electroluminescentlayer may also be formed by a wet process.

Similarly, for the first electrode layer 870 and the second electrodelayer 850, evaporation by resistance heating, EB evaporation,sputtering, a wet process, and the like can be used.

In FIG. 18C, an electrode layer having reflectivity is used for thefirst electrode layer 870, and an electrode layer having alight-transmitting property is used for the second electrode layer 850in the structure of FIG. 18A. Light emitted from the light-emittingelement is reflected by the first electrode layer 870, transmittedthrough the second electrode layer 850, and is emitted to outside.Similarly, in FIG. 18D, an electrode layer having reflectivity is usedfor the first electrode layer 870, and an electrode layer having alight-transmitting property is used for the second electrode layer 850in the structure of FIG. 18B. Light emitted from the light-emittingelement is reflected by the first electrode layer 870, transmittedthrough the second electrode layer 850, and is emitted to outside.

In the display device of this embodiment mode shown in FIG. 1B, lightemitted from the light-emitting element 190 is transmitted and emittedfrom the first electrode layer 396 side in a direction indicated by anarrow in FIG. 1B.

It is effective to provide a passivation film so as to cover the secondelectrode layer 189. The passivation film can be formed by using aninsulating film containing silicon nitride, silicon oxide, siliconoxynitride (SiON), silicon nitride oxide (SiNO), aluminum nitride (AlN),aluminum oxynitride (AlON), aluminum nitride oxide (AlNO) containingmore nitrogen than oxygen, aluminum oxide, diamond-like carbon (DLC), ora nitrogen-containing carbon film (CN), and a single layer or a stackedlayer of the insulating films can be used. Further, a siloxane resin mayalso be used.

At this time, it is preferable to form the passivation film by using afilm with favorable coverage, for which a carbon film, particularly aDLC film is preferably used. A DLC film can be formed in a temperaturerange from a room temperature to 100° C. or lower; therefore, the DLCfilm can be easily formed above the electroluminescent layer 188 with alow heat resistant property. A DLC film can be formed by a plasma CVDmethod (typically, an RF plasma CVD method, a microwave CVD method, anelectron cyclotron resonance (ECR) CVD method, a hot filament CVD methodand the like), a combustion method, a sputtering method, an ion beamevaporation method, a laser evaporation method or the like. As areaction gas for film formation, a hydrogen gas and a carbonhydride-based gas (for example, CH₄, C₂H₂, C₆H₆ and the like) are usedto be ionized by glow discharge, and the ions are accelerated to impactagainst a cathode to which a negative self-bias voltage is applied, toform a film. Further, a CN film may be formed by using a C₂H₂ gas and aN₂ gas as a reaction gas. A DLC film has high blocking effect withrespect to oxygen, thereby oxidization of the electroluminescent layer188 can be suppressed. Therefore, a problem that the electroluminescentlayer 188 is oxidized during a subsequent sealing step can be prevented.

By firmly fixing the substrate 100 over which the light-emitting element190 is formed as described above and a sealing substrate 195 with asealing material 192, the light-emitting element is sealed (see FIG.1B). In the display device of the present invention, the sealingmaterial 192 and the insulating layer 186 are formed apart so as not tocontact with each other. By forming the sealing material 192 and theinsulating layer 186 apart from each other, even when an insulatingmaterial using an organic material having a high moisture absorbingproperty is used for the insulating layer 186, moisture does not easilyenter, and deterioration of the light-emitting element is prevented,thereby improving the reliability of the display device. As the sealingmaterial 192, typically, a visible light curable resin, an ultravioletray curable resin, or a thermosetting resin is preferably used. Forexample, an epoxy resin such as a bisphenol-A liquid resin, abisphenol-A solid resin, a bromine-containing epoxy resin, a bisphenol-Fresin, a bisphenol-AD resin, a phenol resin, a cresol resin, a novolacresin, a cycloaliphatic epoxy resin, an Epi-Bis type epoxy resin, aglycidyl ester resin, a glycidyl amine-based resin, a heterocyclic epoxyresin, or a modified epoxy resin can be used. It is to be noted that aregion surrounded by a sealing material may be filled with a filler 193,and nitrogen or the like may be charged by sealing in a nitrogenatmosphere. Since a bottom emission type is employed in this embodimentmode, the filler 193 is not required to transmit light. However, in acase of extracting light through the filler 193, the filler is requiredto transmit light. Typically, a visible light curable, ultraviolet raycurable, or thermosetting epoxy resin may be used. By the aforementionedsteps, a display device having a display function using a light-emittingelement of this embodiment mode is completed. Further, the filler may bedropped in a liquid state to be filled in the display device.

A droplet-discharge method using a dispenser method is described withreference to FIG. 24. The droplet-discharge method shown in FIG. 24 usesa control device 40, an imaging means 42, a head 43, a filler 33, amarker 35, a marker 45, a barrier layer 34, a sealing material 32, a TFTsubstrate 30, and an opposing substrate 20. The filler 33 is droppedonce or plural times from the head 43 in a closed loop formed by thesealing material 32. In a case where the filler material has highviscosity, the filler is continuously discharged and attached to aformation region in a connected state. In a case where the fillermaterial has low viscosity, the filler is intermittently discharged anddropped as shown in FIG. 24. At this time, the barrier layer 34 may beprovided to prevent that the sealing material 32 reacts with the filler33. Subsequently, the substrates are attached to each other in vacuumand then cured by ultraviolet ray to make a state filled with thefiller. When a substance having a moisture absorbing property such as adrying agent is used as the filler, much higher moisture absorbingeffect can be obtained, thereby preventing deterioration of the element.

A drying agent is provided in an EL display panel to preventdeterioration of the element due to moisture. In this embodiment mode, adrying agent is provided in a concave portion that is formed so as tosurround the pixel region in the sealing substrate so as not to hinder athin design. Further, a drying agent is also formed in a regioncorresponding to a gate wiring layer so that a moisture absorbing areabecomes wide, and thus, moisture can be effectively absorbed. Inaddition, a drying agent is formed over a gate wiring layer which doesnot emit light from itself, therefore, light extraction efficiency isnot reduced, either.

A light-emitting element is sealed by a glass substrate in thisembodiment mode. It is to be noted that sealing treatment is treatmentfor protecting a light-emitting element from moisture, and any of amethod for mechanically sealing the light-emitting element by a covermaterial, a method for sealing the light-emitting element with athermosetting resin or an ultraviolet ray curable resin, and a methodfor sealing the light-emitting element by a thin film having a highbarrier property such as metal oxide or metal nitride is used. As thecover material, glass, ceramics, a plastic, or metal can be used, but amaterial which transmits light is required to be used in a case wherelight is emitted to a cover material side. The cover material and thesubstrate over which the light-emitting element is formed are attachedto each other with a sealing material such as a thermosetting resin oran ultraviolet ray curable resin, and a sealed space is formed by curingthe resin using heat treatment or ultraviolet ray irradiation treatment.It is also effective to provide a moisture absorbing material typifiedby barium oxide in this sealed space. This moisture absorbing materialmay be provided over and in contact with the sealing material, or overthe partition wall or in the periphery of the light-emitting element soas not to shield light from the light-emitting element. Further, thespace between the cover material and the substrate over which thelight-emitting element is formed can be filled with a thermosettingresin or an ultraviolet ray curable resin. In this case, it is effectiveto add a moisture absorbing material typified by barium oxide in thethermosetting resin or the ultraviolet ray curable resin.

FIG. 10 shows an example in which, in the display device shown in FIGS.1A and 1B manufactured in this embodiment mode, the source electrodelayer or the drain electrode layer and the first electrode layer are notdirectly in contact with each other to be electrically connected, andconnected to each other with a wiring layer interposed therebetween. Ina display device in FIG. 10, a source electrode layer or a drainelectrode layer of a thin film transistor for driving a light-emittingelement and a first electrode layer 395 are electrically connected toeach other with a wiring layer 199 interposed therebetween. In FIG. 10,a part of the first electrode layer 395 is stacked over the wiring layer199 to be connected; however, the first electrode layer 395 may beformed first, and then, the wiring layer 199 may be formed over thefirst electrode layer 395 to be in contact.

In this embodiment mode, the terminal electrode layer 178 is connectedto an FPC 194 through an anisotropic conductive layer 196 in theexternal terminal connection region 202, and electrically connected tothe outside. In addition, as shown in FIG. 1A that is a top view of thedisplay device, the display device manufactured in this embodiment modeincludes a peripheral driver circuit region 207 and a peripheral drivercircuit region 208 having a scanning line driver circuit in addition tothe peripheral driver circuit region 204 and the peripheral drivercircuit region 209 having a signal line driver circuit.

The circuits as described above are formed in this embodiment mode;however, the present invention is not limited thereto. An IC chip may bemounted by the aforementioned COG method or TAB method as the peripheraldriver circuit. Further, each of the gate line driver circuit and thesource line driver circuit may be provided in a single number or aplurality of numbers.

In the display device of the present invention, a driving method forimage display is not particularly limited, and for example, a dotsequential driving method, a line sequential driving method, an areasequential driving method and the like may be used. Typically, the linesequential driving method may be used, and a time division gray scaledriving method and an area gray scale driving method may also beappropriately used. Further, a video signal inputted to the source lineof the display device may be an analog signal or a digital signal. Thedriver circuit and the like may be appropriately designed in accordancewith the video signal.

Further, in a display device using a digital video signal, a videosignal that is inputted into a pixel has a constant voltage (CV) or hasa constant current (CC). As for a video signal with a constant voltage(CV), a voltage that is applied to a light-emitting element is constant(CVCV), or a current that is flowed through a light-emitting element isconstant (CVCC). In addition, as for a video signal with a constantcurrent (CC), a voltage that is applied to a light-emitting element isconstant (CCCV), or a current that is flowed through a light-emittingelement is constant (CCCC).

By applying the present invention, a highly reliable display device canbe manufactured. Therefore, a high-definition and high-image qualitydisplay device can be manufactured with high yield.

Embodiment Mode 2

Another embodiment mode of the present invention will be described withreference to FIGS. 7A and 7B, 8, and 9. This embodiment mode shows anexample in which a second interlayer insulating layer is not formed inthe display device manufactured in Embodiment Mode 1. Therefore,explanations of the same portions or portions having the same functionswill be omitted.

As described in Embodiment Mode 1, over a substrate 100, a p-channelthin film transistor 173, an n-channel thin film transistor 174, ann-channel thin film transistor 175, a p-channel thin film transistor176, and an insulating film 168 are formed. In each of the thin filmtransistors, a source electrode layer or a drain electrode layerconnected to a source region or a drain region of a semiconductor layeris formed. A first electrode layer 185 is formed to be in contact with asource electrode layer or a drain electrode layer 172 b in the p-channelthin film transistor 176 provided in a pixel region 206 (see FIG. 7A).

The first electrode layer 185 functions as a pixel electrode, and may beformed by the same material and through the same step as the firstelectrode layer 396 in Embodiment Mode 1. The first electrode layer 185that is a light-transmitting electrode layer may be specifically formedby using a transparent conductive film formed of a light-transmittingconductive material such as indium oxide containing tungsten oxide,indium zinc oxide containing tungsten oxide, indium oxide containingtitanium oxide, indium tin oxide containing titanium oxide, or the like.

Further, silicon oxide may be added into indium oxide containingtungsten oxide, indium zinc oxide containing tungsten oxide, indiumoxide containing titanium oxide, and indium tin oxide containingtitanium oxide. In a sputtering method where a thin film is formed bysputtering a target, unevenness called a nodule is generated on a targetsurface to which sputtering is performed. When a target having such anuneven shape is used, a film with uniform composition cannot be formed,a large lump of a material is generated like a dust in the film, and adense film cannot be obtained. When sputtering is performed by using atarget in which silicon oxide is added into a transparent conductivematerial as described above, unevenness on the target surface can bereduced, and a uniform and dense film can be obtained.

An example of a composition ratio of each light-transmitting conductivematerial is described. In indium oxide containing tungsten oxide, thecomposition ratio of tungsten oxide may be 1.0 wt % and indium oxide maybe 99.0 wt %. In indium zinc oxide containing tungsten oxide, tungstenoxide may be 1.0 wt %, zinc oxide may be 0.5 wt %, and indium oxide maybe 98.5 wt %. In indium oxide containing titanium oxide, titanium oxidemay be 1.0 to 5.0 wt % and indium oxide may be 99.0 to 95.0 wt %. Inindium tin oxide (ITO), tin oxide may be 10.0 wt % and indium oxide maybe 90.0 wt %. In indium zinc oxide (IZO), zinc oxide may be 10.7 wt %and indium oxide may be 89.3 wt %. Further, in indium tin oxidecontaining titanium oxide, titanium oxide may be 5.0 wt %, tin oxide maybe 10.0 wt %, and indium oxide may be 85.0 wt %. The composition ratiosas described above are just examples, and a composition ratio may be setappropriately.

The first electrode layer 185 can be formed by an evaporation method, asputtering method, or the like. In a case of using a sputtering method,a gas containing water (H₂O) or H₂ may be used as a gas. In thisembodiment mode, the first electrode layer 185 is formed by using indiumzinc oxide containing silicon oxide and tungsten oxide by a sputteringmethod using a gas containing water (H₂O) or H₂. The first electrodelayer 185 may be preferably formed in a total thickness range of 100 to800 nm, and is 185 nm in this embodiment mode. In this embodiment mode,a gas containing 50 sccm of argon (Ar), 1.0 sccm of oxygen (O₂), and 0.2sccm of H₂ is used. In a case of using an H₂O gas, the flow rate ispreferably 0.5 sccm or less. The indium zinc oxide film containingsilicon oxide and tungsten oxide formed in this embodiment mode hasfavorable processability, and can be etched without leaving a residue bywet etching using weak acid. When such a film is used for a pixelelectrode of a display device, a highly reliable display device can bemanufactured, in which light extraction efficiency of a light-emittingelement is favorable, and defects due to an etching defect of anelectrode or the like are suppressed.

An insulating layer 186 is formed so as to cover an end portion of thefirst electrode layer 185 and the thin film transistors (see FIG. 7B).Acrylic is used for the insulating layer 186 in this embodiment mode. Anelectroluminescent layer 188 is formed over the first electrode layer185, a second electrode layer 189 is formed thereover, and alight-emitting element 190 is formed. A terminal electrode layer 178 isattached to an FPC 194 through an anisotropic conductive layer 196 in anexternal terminal connection region 202. The substrate 100 is attachedto a sealing substrate 195 with a sealing material 192, and the insideof the display device is filled with a filler 193 (see FIG. 8). In thedisplay device of the present invention, the sealing material 192 andthe insulating layer 186 are formed apart so as not to be in contactwith each other. When the sealing material 192 and the insulating layer186 are formed apart as described above, moisture does not easily enter,deterioration of the light-emitting element is prevented, andreliability of the display device can be improved, even in a case wherean insulating material using an organic material having a high moistureabsorbing property is used for the insulating layer 186.

In a display device shown in FIG. 9, a first electrode layer 397 isselectively formed over the insulating film 168 before forming thesource electrode layer or the drain electrode layer 172 b connected tothe p-channel thin film transistor 176. In this case, the sourceelectrode layer or the drain electrode layer 172 b and the firstelectrode layer 397 are connected to each other so that the sourceelectrode layer or the drain electrode layer 172 b is stacked over thefirst electrode layer 397 in this embodiment mode. When the firstelectrode layer 397 is formed before the source electrode layer or thedrain electrode layer 172 b, the first electrode layer 397 can be formedover a flat formation region, and coverage is favorable. Moreover, thereis an advantage that the first electrode layer 397 can be formed withfavorable planarity because polishing treatment such as CMP can besufficiently performed.

By applying the present invention, a highly reliable display device canbe manufactured. Therefore, a high-definition and high-image qualitydisplay device can be manufactured with high yield.

Embodiment Mode 3

A display device in this embodiment mode will be described withreference to FIGS. 11A and 11B.

As shown in FIGS. 11A and 11B, a display device described in thisembodiment mode is a top emission display device in which light isextracted through a sealing substrate. In display devices shown in FIGS.11A and 11B, electrode structures of light-emitting elements aredifferent from each other.

In the display device in FIG. 11A, over a substrate 600, base films 601a and 601 b, a thin film transistor 605, a gate insulating layer 602,insulating layers 603, 606, and 607, an insulating layer 609 functioningas a partition wall, a first electrode layer 610, a transparentconductive film 615, an electroluminescent layer 611, a second electrodelayer 612, and a protective film 613 are provided. The thin filmtransistor 605 includes a semiconductor layer, which has impurityregions functioning as a source region and a drain region, the gateinsulating layer 602, a gate electrode layer having a stacked structureof two layers, and a source electrode layer and a drain electrode layer.The source electrode layer or the drain electrode layer is in contactwith and electrically connected to the impurity region of thesemiconductor layer and the first electrode layer 610.

In the display device of this embodiment mode, a reflective electrodelayer having reflectivity is used for the first electrode layer 610, alight-transmitting electrode layer is used for the second electrodelayer 612, and light emitted from a light-emitting element 614 isreflected. Therefore, light is emitted from a side of the secondelectrode layer 612 in a direction indicated by an arrow. As describedabove, a reflective electrode layer used for a pixel electrode layer ofa light-emitting element is required to have high reflectivity andfavorable planarity of a surface. The first electrode layer 610 and thetransparent conductive film 615 form a stacked structure. The firstelectrode layer 610 is formed by using a reflective film, and thetransparent conductive film 615 and the second electrode layer 612 areformed by using an IWZO film. As shown in FIG. 11A, by stacking thetransparent conductive film 615, the first electrode layer 610 can beprotected, and thus, there is an advantage that the yield can beimproved.

In this embodiment mode, the substrate 600 is a glass substrate, thebase film 601 a is a silicon nitride oxide film, the base film 601 b isa silicon oxynitride film, the gate insulating layer 602 is a siliconoxynitride film, the insulating layer 603 is a silicon nitride oxidefilm, the insulating layer 606 is a silicon oxide film, the insulatinglayer 607 is a siloxane resin film, the insulating layer 609 functioningas a partition wall is polyimide, and the protective film 613 is asilicon nitride oxide film.

In the display device shown in FIG. 11B, over a substrate 620, basefilms 621 a and 621 b, a thin film transistor 625, a gate insulatinglayer 622, insulating layers 623, 626, and 627, interlayer films 628 and636, an insulating layer 629 functioning as a partition wall, a firstelectrode layer 630, a transparent conductive film 635, anelectroluminescent layer 631, a second electrode layer 632, and aprotective film 633 are provided. The thin film transistor 625 includesa semiconductor layer, which has impurity regions functioning as asource region and a drain region, the gate insulating layer 622, a gateelectrode layer having a stacked structure of two layers, and a sourceelectrode layer and a drain electrode layer. The source electrode layeror the drain electrode layer is in contact with and electricallyconnected to the impurity region of the semiconductor layer and thefirst electrode layer 630.

A light-emitting element 634 of the display device shown in FIG. 11Bincludes the first electrode layer 630, the transparent conductive film635, the electroluminescent layer 631, and the second electrode layer632. The first electrode layer 630 and the transparent conductive film635 form a stacked structure. The first electrode layer 630 is formed byusing a reflective film, and the transparent conductive film 635 isformed by using an IWZO film. As shown in FIG. 11B, by stacking thetransparent conductive film 635, the first electrode layer 630 can beprotected, and thus, there is an advantage that the yield can beimproved. In addition, the second electrode layer 632 shown in FIG. 11Bis formed by using a light-transmitting silver thin film that isthinned.

In this embodiment mode, the transparent conductive film 615, the secondelectrode layer 612, the transparent conductive film 635, and the secondelectrode layer 632 can be formed by the same material and through thesame step as the first electrode layer 396 in Embodiment Mode 1.Specifically, a transparent conductive film formed of alight-transmitting conductive material such as indium oxide containingtungsten oxide, indium zinc oxide containing tungsten oxide, indiumoxide containing titanium oxide, or indium tin oxide containing titaniumoxide may be used.

Further, silicon oxide may be added into indium oxide containingtungsten oxide, indium zinc oxide containing tungsten oxide, indiumoxide containing titanium oxide, and indium tin oxide containingtitanium oxide. In a sputtering method where a thin film is formed bysputtering a target, unevenness called a nodule is generated on a targetsurface to which sputtering is performed. When a target having such anuneven shape is used, a film with uniform composition cannot be formed,a large lump of a material is generated like a dust in the film, and adense film cannot be obtained. When sputtering is performed by using atarget in which silicon oxide is added into a transparent conductivematerial as described above, unevenness on the target surface can bereduced, and a uniform and dense film can be obtained.

In this embodiment mode, the transparent conductive film 615, the secondelectrode layer 612, the transparent conductive film 635, and the secondelectrode layer 632 are formed by using indium zinc oxide containingsilicon oxide and tungsten oxide by a sputtering method using a gascontaining water (H₂O) or H₂. In this embodiment mode, a gas containing50 sccm of argon (Ar), 1.0 sccm of oxygen (O₂), and 0.2 sccm of H₂ isused. In a case of using an H₂O gas, the flow rate is preferably 0.5sccm or less. The indium zinc oxide film containing silicon oxide andtungsten oxide formed in this embodiment mode has favorableprocessability, and can be etched without leaving a residue by wetetching using an etchant such as weak acid. When such a film is used fora pixel electrode of a display device, a highly reliable display devicecan be manufactured, in which light extraction efficiency of alight-emitting element is favorable, and defects due to an etchingdefect of an electrode or the like are suppressed.

The first electrode layers 610 and 630 having reflectivity can be formedby using a conductive film formed of titanium, tungsten, nickel, gold,platinum, silver, aluminum, magnesium, calcium, lithium, or alloythereof.

Other components shown in FIG. 11B may be formed by the same materialand the same step as those of FIG. 11A. Further, in the display deviceshown in FIG. 11B, the interlayer film 628 is a silicon nitride oxidefilm, and the interlayer film 636 is a titanium nitride film. When theinterlayer films 628 and 636 are formed between the insulating layer 627and the first electrode layer 630, adhesion of the insulating layer 627and the first electrode layer 630 can be improved. Further, the titaniumnitride film can also have a function of preventing static electricity.A siloxane resin film used for the insulating layer 627 may also beformed in a thickness thinner than the insulating layer 627 between thesilicon nitride oxide film used as the interlayer film 628 and thetitanium nitride film.

As described above, by applying the present invention, a highly reliabledisplay device can be manufactured. Therefore, a high-definition andhigh-image quality display device can be manufactured with high yield.

Embodiment Mode 4

Another embodiment mode of the present invention will be described withreference to FIGS. 13A to 13C. This embodiment mode shows an example inwhich a structure of a gate electrode layer of a thin film transistor isdifferent from the one of the display device manufactured in EmbodimentMode 1. Therefore, explanations of the same portions or portions havingthe same functions will be omitted.

FIGS. 13A to 13C show display devices in a manufacturing step, whichcorrespond to the display device of FIG. 4B shown in Embodiment Mode 1.

In FIG. 13A, thin film transistors 273 and 274 are provided in aperipheral driver circuit region 214, and thin film transistors 275 and276 are provided in a pixel region 216. A gate electrode layer of thethin film transistor in FIG. 13A is formed by a stacked structure of twoconductive films, and the upper gate electrode layer is processed tohave a width narrower than that of the lower gate electrode layer. Thelower gate electrode layer has a taper shape, and the upper gateelectrode layer has a shape in which an angle of a side surface isalmost perpendicular. As described here, the gate electrode layer mayhave a taper shape, or a shape without a taper portion, in which anangle of a side surface is almost perpendicular.

In FIG. 13B, thin film transistors 373 and 374 are provided in theperipheral driver circuit region 214, and thin film transistors 375 and376 are provided in the pixel region 216. A gate electrode layer of thethin film transistor in FIG. 13B is also formed by a stacked structureof two conductive films, and the upper gate electrode layer and thelower gate electrode layer have a continuous taper shape.

In FIG. 13C, thin film transistors 473 and 474 are provided in theperipheral driver circuit region 214, and thin film transistors 475 and476 are provided in the pixel region 216. A gate electrode layer of thethin film transistor in FIG. 13C has a single layer structure and ataper shape. The gate electrode layer may also have a single layerstructure like this.

In the display device shown in FIG. 13C, a gate insulating layer isformed by a gate insulating layer 477 and a gate insulating layer 478that is selectively provided over the gate insulating layer 477. In sucha manner, the gate insulating layer 478 may be selectively providedbelow the gate electrode layer, and an end portion thereof may have ataper shape. In FIG. 13C, both of the end portion of the gate insulatinglayer 478 and an end portion of the gate electrode layer that is formedover the gate insulating layer 478 have a taper shape, and are formedcontinuously; however, they may also be formed discontinuously so as tohave a step. In this embodiment mode, the gate insulating layer 477 isformed by using a silicon oxynitride film and the gate insulating layer478 is formed by using a silicon nitride film.

As described above, the gate electrode layer can have various structuresin accordance with a configuration and a shape thereof. Therefore, adisplay device to be manufactured has also various structures. When animpurity region in a semiconductor layer is formed in a self-alignmentmanner using the gate electrode layer as a mask, a structure or aconcentration distribution of the impurity region is changed dependingon the structure of the gate electrode layer. By designing inconsideration with the above matters, a thin film transistor having adesired function can be manufactured.

This embodiment mode can be implemented in combination with each ofEmbodiment Modes 1 to 3.

Embodiment Mode 5

In this embodiment mode, an example of a dual emission display devicewill be described with reference to FIG. 12.

FIG. 12 shows a display device, which includes an element substrate1300, thin film transistors 1355, 1365, 1375 and 1385, a sourceelectrode layer or a drain electrode layer 1328, conductive layers 1327a and 1327 b, a first electrode layer 1317, an electroluminescent layer1319, a second electrode layer 1320, a protective layer 1321, a filler1322, a sealing material 1325, a gate insulating layer 1310, insulatinglayers 1311, 1312 and 1314, a sealing substrate 1323, a wiring layer1345, a terminal electrode layer 1381, an anisotropic conductive layer1382, and an FPC 1383. The display device also includes a separationregion 221, an external terminal connection region 222, a wiring region223, a peripheral driver circuit region 224, and a pixel region 226. Thefiller 1322 can be formed by a droplet-discharge method by being madeinto a liquid composition as in the droplet-discharge method shown inFIG. 24. The element substrate 1300 in which the filler is formed by adroplet-discharge method and the sealing substrate 1323 are attached toeach other to seal the peripheral driver circuit region 224, the pixelregion 226 and the like.

The display device in FIG. 12 is a dual emission type, in which light isemitted from both the element substrate 1300 side and the sealingsubstrate 1323 side in directions indicated by arrows. Therefore, alight-transmitting electrode layer is used for both the first electrodelayer 1317 and the second electrode layer 1320.

In the present invention, the first electrode layer 1317 and the secondelectrode layer 1320, each of which is a light-transmitting electrodelayer, may be specifically formed by using a transparent conductive filmformed of a light-transmitting conductive material, and indium oxidecontaining tungsten oxide, indium zinc oxide containing tungsten oxide,indium oxide containing titanium oxide, indium tin oxide containingtitanium oxide, and the like can be used.

Further, silicon oxide may be added into indium oxide containingtungsten oxide, indium zinc oxide containing tungsten oxide, indiumoxide containing titanium oxide, and indium tin oxide containingtitanium oxide. In a sputtering method where a thin film is formed bysputtering a target, unevenness called a nodule is generated on a targetsurface to which sputtering is performed. When a target having such anuneven shape is used, a film with uniform composition cannot be formed,a large lump of a material is generated like a dust in the film, and adense film cannot be obtained. When sputtering is performed by using atarget in which silicon oxide is added into a transparent conductivematerial as described above, unevenness on the target surface can bereduced, and a uniform and dense film can be obtained.

An example of a composition ratio of each light-transmitting conductivematerial is described. In indium oxide containing tungsten oxide, thecomposition ratio of tungsten oxide may be 1.0 wt % and indium oxide maybe 99.0 wt %. In indium zinc oxide containing tungsten oxide, tungstenoxide may be 1.0 wt %, zinc oxide may be 0.5 wt %, and indium oxide maybe 98.5 wt %. In indium oxide containing titanium oxide, titanium oxidemay be 1.0 to 5.0 wt % and indium oxide may be 99.0 to 95.0 wt %. Inindium tin oxide (ITO), tin oxide may be 10.0 wt % and indium oxide maybe 90.0 wt %. In indium zinc oxide (IZO), zinc oxide may be 10.7 wt %and indium oxide may be 89.3 wt %. Further, in indium tin oxidecontaining titanium oxide, titanium oxide may be 5.0 wt %, tin oxide maybe 10.0 wt %, and indium oxide may be 85.0 wt %. The composition ratiosas described above are just examples, and a composition ratio may be setappropriately.

In this embodiment mode, the first electrode layer 1317 and the secondelectrode layer 1320 are formed by using indium zinc oxide containingsilicon oxide and tungsten oxide by a sputtering method using a gascontaining water (H₂O) or H₂. In this embodiment mode, a gas containing50 scan of argon (Ar), 1.0 sccm of oxygen (O₂), and 0.2 sccm of H₂ isused. In a case of using an H₂O gas, the flow rate is preferably 0.5sccm or less. The indium zinc oxide film containing silicon oxide andtungsten oxide formed in this embodiment mode has favorableprocessability, and can be etched without leaving a residue by wetetching using an etchant such as weak acid.

In addition, even in a case of a non-light-transmitting material such asa metal film, when the thickness is made thin (preferably, about 5 to 30nm) so as to be able to transmit light, light can be emitted from thefirst electrode layer 1317 and the second electrode layer 1320. As ametal thin film that can be used for the first electrode layer 1317 andthe second electrode layer 1320, a conductive film formed of titanium,tungsten, nickel, gold, platinum, silver, aluminum, magnesium, calcium,lithium, and an alloy thereof can be used.

As described above, in the display device in FIG. 12, light emitted fromthe light-emitting element 1305 passes through both the first electrodelayer 1317 and the second electrode layer 1320 to have a structure wherelight is emitted from both sides.

This embodiment mode can be implemented in combination with each ofEmbodiment Modes 1 to 4.

In the display device of this embodiment mode, the source electrodelayer or the drain electrode layer 1328 of the thin film transistor 1355and the first electrode layer 1317 of the light-emitting element 1305,which is a pixel electrode layer, are not directly stacked to beelectrically connected, but the source electrode layer or the drainelectrode layer 1328 and the first electrode layer 1317 are electricallyconnected to each other with the conductive layers 1327 a and 1327 binterposed therebetween. In such a structure, materials by which thesource electrode layer or the drain electrode layer and the firstelectrode layer are not easily electrically connected to each other whenboth electrode layers are directly in contact with each other, ormaterials by which deterioration such as electric erosion is caused whenboth electrode layers are in contact with each other can also be usedsince a conductive layer is interposed between both electrode layers.Therefore, a range of a choice for materials that can be used for thesource electrode layer or the drain electrode layer and the firstelectrode layer can be wide. Since it is not necessary to consider aproblem which arises when the source electrode layer or the drainelectrode layer and the first electrode layer are stacked, a materialprovided with a property required for each of the source electrode layeror the drain electrode layer and the first electrode layer can be freelyselected. Therefore, a much higher-functional and reliable displaydevice can be manufactured with high yield.

Embodiment Mode 6

An example of providing a protective diode for a scanning line inputterminal portion and a signal line input terminal portion will bedescribed with reference to FIG. 15. In FIG. 15, a pixel 2702 isprovided with TFTs 501 and 502, a capacitor element 504, and alight-emitting element 503. These TFTs have similar structures to thoseof Embodiment Mode 1.

Protective diodes 561 and 562 are provided in the signal line inputterminal portion. These protective diodes are manufactured throughsimilar steps to the TFTs 501 and 502, and a gate is connected to one ofa drain and a source to operate as a diode. FIG. 14 shows an equivalentcircuit diagram of a top view of FIG. 15.

The protective diode 561 includes a gate electrode layer, asemiconductor layer, and a wiring layer. The protective diode 562 has asimilar structure. Common potential lines 554 and 555 connected to theseprotective diodes are formed of the same layer as the gate electrodelayer. Accordingly, a contact hole is required to be formed in aninsulating layer so that the common potential line is electricallyconnected to the wiring layer.

A contact hole in the insulating layer may be formed by forming a masklayer and performing etching. In this case, by performing etching ofatmospheric pressure discharge, local electric discharge can beperformed, and a mask layer is not required to be formed over the entiresurface of the substrate.

A signal wiring layer is formed of the same layer as a source and drainwiring layer 505 in the TFT 501, and the signal wiring layer connectedto the source and drain wiring layer 505 and the source or drain sideare connected to each other.

An input terminal portion on the scanning signal line side also has asimilar structure. A protective diode 563 includes a gate electrodelayer, a semiconductor layer, and a wiring layer. A protective diode 564has a similar structure. Common potential lines 556 and 557 connected tothese protective diodes are formed of the same layer as the sourceelectrode layer and the drain electrode layer. The protective diodesprovided in the input stage can be formed at the same time. It is to benoted that the protective diode is not limited to be arranged at aposition shown in this embodiment mode, but may also be arranged betweena driver circuit and a pixel.

Embodiment Mode 7

A television device can be completed by a display device formed inaccordance with the present invention. FIG. 23 is a block diagramshowing a main structure of the television device (EL television devicein this embodiment mode). A display panel can be formed in any manner asfollows: as the structure shown in FIG. 16A, only a pixel portion 701 isformed, and a scanning line driver circuit 703 and a signal line drivercircuit 702 are mounted by a TAB method as shown in FIG. 17B or by a COGmethod as shown in FIG. 17A; a TFT is formed, and a pixel portion 701and a scanning line driver circuit 703 are formed to be integrated overa substrate, and a signal line driver circuit 702 is separately mountedas a driver IC as shown in FIG. 16B; a pixel portion 701, a signal linedriver circuit 702, and a scanning line driver circuit 703 are formed tobe integrated over the substrate as shown in FIG. 16C; or the like.

Another structure of an external circuit includes, on the input side ofthe video signal, a video signal amplifier circuit 705 which amplifies avideo signal among signals received by a tuner 704; a video signalprocessing circuit 706 which converts the signal output into achrominance signal corresponding to each color of red, green, and blue;a control circuit 707 which converts the video signal into an inputspecification of a driver IC; and the like. The control circuit 707outputs the signal into the scanning line side and the signal line side,respectively. In a case of digital driving, a signal dividing circuit708 may be provided on the signal line side so that an input digitalsignal is supplied by dividing into m-pieces.

Among signals received by the tuner 704, an audio signal is transmittedto an audio signal amplifier circuit 709, and the output thereof issupplied to a speaker 713 through an audio signal processing circuit710. The control circuit 711 receives control information on a receivingstation (a receiving frequency) or sound volume from an input portion712 and transmits the signal to the tuner 704 or the audio signalprocessing circuit 710.

As shown in FIGS. 20A and 20B, a television device can be completed byincorporating a display module into a chassis. The display panel inwhich components up to an FPC are attached as shown in FIGS. 1A and 1Bis generally called an EL display module. An EL television device can becompleted when the EL display module as in FIGS. 1A and 1B is used. Amain screen 2003 is formed by using the display module, and a speakerunit 2009, operation switches, and the like are provided as otherattached equipments. In such a manner, the television device can becompleted in accordance with the present invention.

In addition, reflected light of light entered from the outside may beshielded by using a wave plate or a polarizing plate. In a case of a topemission display device, an insulating layer to be a partition wall maybe colored and used as a black matrix. The partition wall can be formedby a droplet-discharge method or the like, and a resin material such asa black pigment resin or polyimide may be mixed with carbon black or thelike. A stacked layer thereof may also be used. Further, by adroplet-discharge method, different materials may be discharged on thesame region plural times to form a partition wall. λ/4 and λ/2 platesmay be used as wave plates and may be designed to be able to controllight. As a structure, a TFT element substrate, a light-emittingelement, a sealing substrate (sealing material), wave plates (λ/4 andλ/2 plates), a polarizing plate are stacked in this order, in whichlight emitted from the light-emitting element is emitted outside fromthe polarizing plate side through the above components. The wave platesor the polarizing plate may be provided on a side to which light isemitted or may be provided on both sides in a case of a dual emissiontype display device in which light is emitted to both sides. Inaddition, an anti-reflective film may be provided on the outer side ofthe polarizing plate. Consequently, a much higher-definition andaccurate image can be displayed.

As shown in FIG. 20A, a display panel 2002 using a display element isincorporated into a chassis 2001. By using a receiver 2005, in additionto reception of general TV broadcast, information communication can alsobe carried out in one direction (from a transmitter to a receiver) or inboth directions (between a transmitter and a receiver or betweenreceivers) by connecting to a communication network by a fixed line orwirelessly through a modem 2004. The operation of the television devicecan be carried out by switches incorporated in the chassis or by aremote control device 2006, which is separated from the main body. Adisplay portion 2007 that displays information to be outputted may alsobe provided in this remote control device.

In addition, in the television device, a structure for displaying achannel, sound volume, or the like may be additionally provided byforming a sub-screen 2008 with a second display panel in addition to themain screen 2003. In this structure, the main screen 2003 may be formedof an EL display panel superior in a viewing angle, and the sub-screenmay be formed of a liquid crystal display panel capable of display withlow power consumption. In order to prioritize low power consumption, astructure in which the main screen 2003 is formed of a liquid crystaldisplay panel, the sub-screen is formed of an EL display panel, and thesub-screen is able to flash on and off may also be employed. Obviously,both of the main-screen and the sub-screen may be formed by using an ELdisplay panel in accordance with the present invention. By the presentinvention, a highly reliable display device can be manufactured even byusing such a large substrate with many TFTs and electronic parts.

FIG. 20B shows a television device having a large display portion of,for example, 20 to 80 inches, which includes a chassis 2010, a keyboard2012 which is an operation portion, a display portion 2011, a speakerunit 2013, and the like. The present invention is applied to manufacturethe display portion 2011. FIG. 20B shows a television device having acurved display portion because a bendable substance is used for thedisplay portion. The shape of the display portion can be freely designedin this manner, and thus, a television device having a desired shape canbe manufactured.

In accordance with the present invention, a display device can bemanufactured through a simplified process, and thus, the cost can bereduced. Hence, even a television device with a large screen displayportion can be formed at low cost by applying the present invention.Accordingly, a high-performance and highly reliable television devicecan be manufactured with high yield.

The present invention is not limited to the television device and isalso applicable to various usages such as display mediums having a largearea, for example, a monitor of a personal computer, an informationdisplay board at a train station, an airport, or the like, or anadvertisement display board on the street.

Embodiment Mode 8

This embodiment mode will be described with reference to FIGS. 21A and21B. This embodiment mode shows an example of a module to which a panelhaving a display device manufactured in Embodiment Modes 1 to 7 isapplied.

An information terminal module shown in FIG. 21A includes a printedwiring board 946 over which a controller 901, a central processing unit(CPU) 902, a memory 911, a power source circuit 903, an audio processingcircuit 929, a transmission/reception circuit 904, and other elementssuch as a resistor, a buffer, and a capacitor element are mounted.Further, a panel 900 is connected to the printed wiring board 946through a flexible printed circuit (FPC) 908.

The panel 900 includes a pixel portion 905 in which each pixel has alight-emitting element, a first scanning line driver circuit 906 a and asecond scanning line driver circuit 906 b which select a pixel in thepixel portion 905, and a signal line driver circuit 907 which supplies avideo signal to the selected pixel.

Various control signals are inputted and outputted through an interface(I/F) 909 provided over the printed wiring board 946. An antenna port910 for transmitting and receiving signals with an antenna is providedover the printed wiring board 946.

It is to be noted that the printed wiring board 946 is connected to thepanel 900 through the FPC 908 in this embodiment mode; however, thepresent invention is not limited to this structure. The controller 901,the audio processing circuit 929, the memory 911, the CPU 902 or thepower source circuit 903 may be directly mounted on the panel 900 by aCOG (Chip on Glass) method. Further, various elements such as acapacitor element and a buffer are provided over the printed wiringboard 946, thereby preventing a noise from occurring in the power sourcevoltage and signals, and the signal rise time from becoming slow.

FIG. 21B is a block diagram of the module shown in FIG. 21A. This module999 includes a VRAM 932, a DRAM 925, a flash memory 926 and the like asthe memory 911. The VRAM 932 stores data on the image to be displayed ona panel, the DRAM 925 stores image data or audio data, and the flashmemory 926 stores various programs.

The power source circuit 903 generates a power source voltage applied tothe panel 900, the controller 901, the CPU 902, the audio processingcircuit 929, the memory 911, and the transmission/reception circuit 931.There is a case where a current source is provided in the power sourcecircuit 903 depending on the specifications of the panel.

The CPU 902 includes a control signal generating circuit 920, a decoder921, a register 922, an arithmetic circuit 923, a RAM 924, an interface935 for the CPU and the like. Various signals inputted to the CPU 902through the interface 935 are held in the register 922, and theninputted to the arithmetic circuit 923, the decoder 921 and the like. Inthe arithmetic circuit 923, an arithmetic operation is performed basedon the inputted signal, and the address of various instructions isdetermined. Meanwhile, a signal inputted to the decoder 921 is decodedand inputted to the control signal generating circuit 920. The controlsignal generating circuit 920 generates a signal containing variousinstructions based on the inputted signal, and then transmits thesignals to the address determined by the arithmetic circuit 923,specifically, the memory 911, the transmission/reception circuit 931,the audio processing circuit 929, the controller 901 or the like.

Each of the memory 911, the transmission/reception circuit 931, theaudio processing circuit 929, and the controller 901 operates inaccordance with the received instruction. The operation thereof isbriefly described below.

A signal inputted from an input means 930 is transmitted to the CPU 902which is mounted on the printed wiring board 946 through the interface909. The control signal generating circuit 920 converts the image datastored in the VRAM 932 into a predetermined format based on the signaltransmitted from the input means 930 such as a pointing device or akeyboard, and transmits the data to the controller 901.

The controller 901 processes the signals containing image datatransmitted from the CPU 902 in accordance with the specifications ofthe panel, and then transmits the signals to the panel 900. Further, thecontroller 901 generates an Hsync signal, a Vsync signal, a clock signalCLK, an alternating current voltage (AC Cont), and a switching signalL/R based on the power source voltage inputted from the power sourcecircuit 903 and the various signals inputted from the CPU 902, andsupplies the signals to the panel 900.

The transmission/reception circuit 904 processes signals which aretransmitted and received as electromagnetic waves by an antenna 933.Specifically, the transmission/reception circuit 904 includes highfrequency circuits such as an isolator, a band pass filter, a VCO(Voltage Controlled Oscillator), an LPF (Low Pass Filter), a coupler,and a balun. A signal containing audio information among the signalstransmitted and received by the transmission/reception circuit 904 istransmitted to the audio processing circuit 929 in accordance with theinstruction of the CPU 902.

The signal containing audio information transmitted in accordance withthe instruction of the CPU 902 is demodulated into an audio signal bythe audio processing circuit 929 and transmitted to a speaker 928. Anaudio signal transmitted from a microphone 927 is modulated by the audioprocessing circuit 929 and transmitted to the transmission/receptioncircuit 904 in accordance with the instruction of the CPU 902.

The controller 901, the CPU 902, the power source circuit 903, the audioprocessing circuit 929, and the memory 911 can be mounted as a packageof this embodiment mode. This embodiment mode can be applied to anycircuits but a high frequency circuit such as an isolator, a band passfilter, a VCO (Voltage Controlled Oscillator), an LPF (Low Pass Filter),a coupler, or a balun.

Embodiment Mode 9

This embodiment mode will be described with reference to FIGS. 21A and21B, and 22. FIG. 22 shows an example of a wireless portable compactphone (mobile phone) including a module manufactured in this embodimentmode 9. A panel 900 is incorporated into a housing 1001 to be detachableso as to be easily in combination with a module 999. The shape and sizeof the housing 1001 can be appropriately changed in accordance with anelectronic device which is incorporated.

The housing 1001 to which the panel 900 is fixed is mounted on a printedwiring board 946 and completed as a module. Over the printed wiringboard 946, a controller, a CPU, a memory, a power source circuit, andother elements such as a resistor, a buffer, and a capacitor element aremounted. Further, an audio processing circuit including a microphone 994and a speaker 995, and a signal processing circuit 993 such as atransmission/reception circuit are provided. The panel 900 is connectedto the printed wiring board 946 through an FPC 908.

Such a module 999, an input means 998, and a buttery 997 are stored in achassis 996. A pixel portion of the panel 900 is arranged to be seenfrom an opening window formed in the chassis 996.

The chassis 996 shown in FIG. 22 is an example of an external appearanceof a phone. However, an electronic device in accordance with thisembodiment mode may be changed into various modes depending on thefunction and application. An example of the modes will be described inthe following embodiment mode.

Embodiment Mode 10

By applying the present invention, various display devices can bemanufactured. In other words, the present invention can be applied tovarious electronic devices into which the various display devices areincorporated as a display portion.

Such electronic devices include a camera such as a video camera or adigital camera, a projector, a head mount display (a goggle typedisplay), a car navigation, a car stereo, a personal computer, a gamemachine, a mobile information terminal (a mobile computer, a mobilephone, an electronic book, or the like), an image reproducing deviceequipped with a recording medium (specifically, a device for reproducinga recording medium such as Digital Versatile Disc (DVD) and including adisplay for displaying the image), and the like. FIGS. 19A to 19D showexamples thereof.

FIG. 19A shows a computer, which includes a main body 2101, a chassis2102, a display portion 2103, a keyboard 2104, an external connectionport 2105, a pointing mouse 2106, and the like. By the presentinvention, a highly reliable computer which displays an image with highquality can be manufactured even when the computer becomes compact and apixel thereof becomes minute.

FIG. 19B shows an image reproducing device equipped with a recordingmedium (specifically a DVD reproducing device), which includes a mainbody 2201, a chassis 2202, a display portion A 2203, a display portion B2204, a recording medium (such as a DVD) reading portion 2205, operationkeys 2206, a speaker portion 2207 and the like. The display portion A2203 mainly displays image information and the display portion B 2204mainly displays character information. By the present invention, ahighly reliable image reproducing device which displays an image withhigh quality can be manufactured even when the image reproducing devicebecomes compact and a pixel thereof becomes minute.

FIG. 19C shows a mobile phone, which includes a main body 2301, an audiooutput portion 2302, an audio input portion 2303, a display portion2304, operation switches 2305, an antenna 2306, and the like. By thepresent invention, a highly reliable mobile phone which displays animage with high quality can be manufactured even when the mobile phonebecomes compact and a pixel thereof becomes minute.

FIG. 19D shows a video camera, which includes a main body 2401, adisplay portion 2402, a chassis 2403, an external connection port 2404,a remote control receiving portion 2405, an image receiving portion2406, a battery 2407, an audio input portion 2408, an eyepiece 2409,operation keys 2410, and the like. By the present invention, a highlyreliable video camera which displays an image with high quality can bemanufactured even when the video camera becomes compact and a pixelthereof becomes minute. This embodiment mode can be arbitrarily combinedwith each of the above embodiment modes.

Embodiment Mode 11

In this embodiment mode, other structures which can be applied to alight-emitting element of the present invention will be described withreference to FIGS. 29A to 29C, and 30A to 30C.

Light-emitting elements utilizing electroluminescence are classifiedaccording to whether a light-emitting material is an organic compound oran inorganic compound, and generally, the former is referred to as anorganic EL element and the latter is referred to as an inorganic ELelement.

Inorganic EL elements are classified into a dispersion-type inorganic ELelement and a thin film inorganic EL element depending on an elementstructure. The elements of the both types are different in that thedispersion-type inorganic EL element has an electroluminescent layer inwhich particles of a light-emitting material are dispersed in a binder,and the thin film inorganic EL element has an electroluminescent layerformed by a thin film of a light-emitting material. However, there is acommon point that electrons accelerated by a high electric field arerequired by the both elements. As a mechanism of light emission that isobtained, donor-acceptor recombination emission utilizing a donor leveland an acceptor level, and localized emission utilizing an inner-shellelectron transition of a metal ion are given. In general, the dispersiontype inorganic EL element exhibits donor-acceptor recombinationemission, and the thin film inorganic EL element exhibits localizedemission.

A light-emitting material that can be used in the present invention iscomposed of a host material and an impurity element serving as alight-emission center. By changing an impurity element that iscontained, light-emission of various colors can be obtained. As a methodfor manufacturing a light-emitting material, various methods such as asolid phase method and a liquid phase method (coprecipitation method)can be used. In addition, a liquid phase method such as a spraypyrolysis method, a double decomposition method, a method by precursorpyrolysis, a reverse micelle method, a method in which the above methodand high-temperature baking are combined, or a freeze-drying method canalso be used.

The solid phase method is a method in which a host material and animpurity element or a compound containing an impurity element areweighed, mixed in a mortar, and reacted with each other by heating andbaking in an electric furnace so that the impurity element is made to becontained in the host material. A baking temperature is preferably 700to 1500° C. This is because solid phase reaction is not progressed at atemperature that is too low and the host material is decomposed at atemperature that is too high. Baking may be performed in a powder state;however, it is preferable to perform baking in a pellet state. Thismethod requires baking at a temperature that is comparatively high butis simple, and thus, this method has high productivity and is suitablefor mass production.

The liquid phase method (coprecipitation method) is a method in which ahost material or a compound containing a host material and an impurityelement or a compound containing an impurity element are reacted witheach other in a solution and dried, and then, baked. In this method,particles of the light-emitting material are uniformly dispersed, theparticle has a small diameter, and reaction can be progressed even whena baking temperature is low.

As a host material for the light-emitting material, sulfide, oxide, ornitride can be used. As the sulfide, for example, zinc sulfide (ZnS),cadmium sulfide (CdS), calcium sulfide (CaS), yttrium sulfide (Y₂S₃),gallium sulfide (Ga₂S₃), strontium sulfide (SrS), barium sulfide (BaS),or the like can be used. As the oxide, for example, zinc oxide (ZnO),yttrium oxide (Y₂O₃), or the like can be used. Further, as the nitride,for example, aluminum nitride (AlN), gallium nitride (GaN), indiumnitride (InN), or the like can be used. In addition, zinc selenide(ZnSe), zinc telluride (ZnTe), or the like can also be used. A ternarymixed crystal such as calcium gallium sulfide (CaGa₂S₄), strontiumgallium sulfide (SrGa₂S₄), or barium gallium sulfide (BaGa₂S₄) may alsobe used.

As a light-emission center of the localized emission, manganese (Mn),copper (Cu), samarium (Sm), terbium (Tb), erbium (Er), thulium (Tm),europium (Eu), cerium (Ce), praseodymium (Pr), or the like can be used.As charge compensation, a halogen element such as fluorine (F) orchlorine (Cl) may be added.

On the other hand, as a light-emission center of the donor-acceptorrecombination emission, a light-emitting material containing a firstimpurity element forming a donor level and a second impurity elementforming an acceptor level can be used. As the first impurity element,for example, fluorine (F), chlorine (Cl), aluminum (Al), or the like canbe used. As the second impurity element, for example, copper (Cu),silver (Ag), or the like can be used.

When a light-emitting material for the donor-acceptor recombinationemission is synthesized by the solid phase method, a host material, afirst impurity element or a compound containing a first impurityelement, and a second impurity element or a compound containing a secondimpurity element are each weighed, mixed in a mortar, and heated andbaked in an electric furnace. As the host material, the host material asdescribed above can be used, and as the first impurity element or thecompound containing the first impurity element, for example, fluorine(F), chlorine (Cl), aluminum sulfide (Al₂S₃), or the like can be used.As the second impurity element or the compound containing the secondimpurity element, for example, copper (Cu), silver (Ag), copper sulfide(Cu₂S), silver sulfide (Ag₂S), or the like can be used. A bakingtemperature is preferably 700 to 1500° C. This is because solid phasereaction is not progressed at a temperature that is too low and the hostmaterial is decomposed at a temperature that is too high. Baking may beperformed in a powder state; however, it is preferable to perform bakingin a pellet state.

In addition, as an impurity element in a case of utilizing the solidphase reaction, a compound formed of the first impurity element and thesecond impurity element may also be combined to be used. In such a case,the impurity element can be easily dispersed and the solid phasereaction can be easily progressed, and thus, a uniform light-emittingmaterial can be obtained. Further, since an extra impurity element isnot contained, a light-emitting material with high purity can beobtained. As the compound formed of the first impurity element and thesecond impurity element, for example, copper chloride (CuCl), silverchloride (AgCl), or the like can be used.

It is to be noted that a concentration of these impurity elements may be0.01 to 10 atom % with respect to the host material, and preferably in arange of 0.05 to 5 atom %.

In a case of the thin film inorganic EL element, an electroluminescentlayer is a layer containing the above light-emitting material and can beformed by a vacuum evaporation method such as a resistance heatingevaporation method or an electron beam evaporation (EB evaporation)method, a physical vapor deposition (PVD) method such as a sputteringmethod, a chemical vapor deposition method (CVD) such as an organicmetal CVD method or a hydride transfer low pressure CVD method, anatomic layer epitaxy method (ALE), or the like.

FIGS. 29A to 29C show examples of a thin film inorganic EL element thatcan be used as a light-emitting element. In FIGS. 29A to 29C, thelight-emitting element includes a first electrode layer 50, anelectroluminescent layer 52, and a second electrode layer 53.

The light-emitting elements shown in FIGS. 29B and 29C have a structurein which an insulating layer is provided between the electrode layer andthe electroluminescent layer in the light-emitting element shown in FIG.29A. The light-emitting element shown in FIG. 29B includes an insulatinglayer 54 between the first electrode layer 50 and the electroluminescentlayer 52. The light-emitting element shown in FIG. 29C includes aninsulating layer 54 a between the first electrode layer 50 and theelectroluminescent layer 52, and an insulating layer 54 b between thesecond electrode layer 53 and the electroluminescent layer 52. Asdescribed above, the insulating layer may be provided between theelectroluminescent layer and one of a pair of the electrode layersinterposing the electroluminescent layer, or between theelectroluminescent layer and both of the electrode layers. Theinsulating layer may be a single layer or a stacked layer includingplural layers.

In addition, although the insulating layer 54 is provided to be incontact with the first electrode layer 50 in FIG. 29B, the insulatinglayer and the electroluminescent layer may be provided in the reversedorder, and the insulating layer 54 may be provided to be in contact withthe second electrode layer 53.

In a case of the dispersion type inorganic EL element, particles of alight-emitting material are dispersed in a binder to form anelectroluminescent layer having a film shape. The light-emittingmaterial is processed into particles. When a particle having a desiredsize cannot be sufficiently obtained by a manufacturing method of thelight-emitting material or the like, the light-emitting material iscrushed in a mortar or the like and processed into particles. The binderis a substance for fixing particles of the light-emitting material in adispersed state and keeping a shape as an electroluminescent layer. Thelight-emitting material is uniformly dispersed and fixed in anelectroluminescent layer by the binder.

In a case of the dispersion type inorganic EL element, anelectroluminescent layer can be formed by using a droplet-dischargemethod which can selectively form an electroluminescent layer, aprinting method (screen printing, offset printing, or the like), acoating method such as a spin coating method, a dipping method, adispenser method, or the like. A thickness is not particularly limited,but is preferably in a range of 10 to 1000 nm. Further, in anelectroluminescent layer containing the light-emitting material and thebinder, the ratio of the light-emitting material is preferably 50 wt %or more and 80 wt % or less.

FIGS. 30A to 30C show examples of a dispersion type inorganic EL elementthat can be used as a light-emitting element. The light-emitting elementshown in FIG. 30A has a stacked structure of a first electrode layer 60,an electroluminescent layer 62, and a second electrode layer 63, inwhich the electroluminescent layer 62 includes a light-emitting material61 held by a binder.

As a binder that can be used in this embodiment mode, an insulatingmaterial can be used. More specifically, an organic material, aninorganic material, or a mixed material of an organic material and aninorganic material can be used. As an organic insulating material, thefollowing resin materials can be used: a polymer having a comparativelyhigh dielectric constant such as a cyanoethyl cellulose based resin,polyethylene, polypropylene, a polystyrene based resin, a siliconeresin, an epoxy resin, vinylidene fluoride, or the like. In addition, aheat-resistant high-molecular material such as aromatic polyamide orpolybenzimidazole, or a siloxane resin may also be used. The siloxaneresin is a resin including a Si—O—Si bond. Siloxane has a skeletonstructure formed of a bond of silicon (Si) and oxygen (O). As asubstituent, an organic group containing at least hydrogen (for example,an alkyl group or aromatic hydrocarbon) is used. Alternatively, a fluorogroup may be used as a substituent. In addition, as a substituent, bothof an organic group containing at least hydrogen and a fluoro group mayalso be used. Further, the following resin material may also be used: avinyl resin such as poly(vinyl alcohol) or poly(vinyl butyral), a phenolresin, a novolac resin, an acrylic resin, a melamine resin, an urethaneresin, an oxazole resin (polybenzoxazole), or the like. In addition, forexample, a photo-curable resin or the like can be used. Fine particleshaving a high dielectric constant such as barium titanate (BaTiO₃) orstrontium titanate (SrTiO₃) can also be mixed to these resins moderatelyto adjust a dielectric constant.

An inorganic insulating material contained in the binder can be formedby a material selected from silicon oxide (SiO_(x)), silicon nitride(SiN_(x)), silicon containing oxygen and nitrogen, aluminum nitride(AlN), aluminum containing oxygen and nitrogen or aluminum oxide(Al₂O₃), titanium oxide (TiO₂), BaTiO₃, SrTiO₃, lead titanate (PbTiO₃),potassium niobate (KNbO₃), lead niobate (PbNbO₃), tantalum oxide(Ta₂O₅), barium tantalate (BaTa₂O₆), lithium tantalate (LiTaO₃), yttriumoxide (Y₂O₃), zirconium oxide (ZrO₂), ZnO, and other substancecontaining an inorganic insulating material. When an inorganic materialhaving a high dielectric constant is made to be contained in an organicmaterial (by adding or the like), a dielectric constant of anelectroluminescent layer formed of a light-emitting material and abinder can be more effectively controlled and can be much higher.

In a manufacturing process, a light-emitting material is dispersed in asolution containing a binder. As a solvent of a solution containing abinder that can be used in this embodiment mode, a solvent may beappropriately selected, which can dissolve a binder material and canform a solution having viscosity suitable for a method of forming anelectroluminescent layer (various wet processes) and a desiredthickness. An organic solvent or the like can be used, and when, forexample, a siloxane resin is used as a binder, propylene glycolmonomethyl ether, propylene glycol monomethyl ether acetate (alsoreferred to as PGMEA), 3-methoxy-3-methyl-1-butanol (also referred to asMMB), or the like can be used.

Light-emitting elements shown in FIGS. 30B and 30C have a structure inwhich an insulating layer is provided between an electrode layer and anelectroluminescent layer in a light-emitting element shown in FIG. 30A.The light-emitting element shown in FIG. 30B includes an insulatinglayer 64 between a first electrode layer 60 and an electroluminescentlayer 62. The light-emitting element shown in FIG. 30C includes aninsulating layer 64 a between the first electrode layer 60 and theelectroluminescent layer 62, and an insulating layer 64 b between thesecond electrode layer 63 and the electroluminescent layer 62. Asdescribed above, the insulating layer may be provided between theelectroluminescent layer and one of a pair of the electrode layersinterposing the electroluminescent layer, or between theelectroluminescent layer and both of the electrode layers. Theinsulating layer may be a single layer or a stacked layer includingplural layers.

In addition, although the insulating layer 64 is provided to be incontact with the first electrode layer 60 in FIG. 30B, the insulatinglayer and the electroluminescent layer may be provided in the reversedorder, and the insulating layer 64 may be provided to be in contact withthe second electrode layer 63.

An insulating layer such as the insulating layer 54 in FIGS. 29B and 29Cor the insulating layer 64 in FIGS. 30B and 30C has no particularlimitation, but preferably has a high insulating resistant property anddense film quality, furthermore, a high dielectric constant. Forexample, silicon oxide (SiO_(x)), yttrium oxide (Y₂O₃), titanium oxide(TiO₂), aluminum oxide (Al₂O₃), hafnium oxide (HfO₂), tantalum oxide(Ta₂O₅), barium titanate (BaTiO₃), strontium titanate (SrTiO₃), leadtitanate (PbTiO₃), silicon nitride (Si₃N₄), zirconium oxide (ZrO₂), orthe like, or a mixed film of the material or a stacked film includingtwo or more kinds of the materials can be used. These insulating filmscan be formed by sputtering, evaporation, CVD, or the like. In addition,the insulating layer may be formed by dispersing particles of theinsulating material in a binder. A binder material may be formed by thesame material and the same method as a binder contained in theelectroluminescent layer. A thickness is not particularly limited, butis preferably in a range of 10 to 1000 nm.

The light-emitting element described in this embodiment mode emits lightby applying a voltage between a pair of the electrode layers interposingthe electroluminescent layer, and can be operated by either DC drivingor AC driving.

In the present invention, a transparent conductive film formed of alight-transmitting conductive material may be used for one or both of apair of the electrode layers of the light-emitting element, and indiumoxide containing tungsten oxide, indium zinc oxide containing tungstenoxide, indium oxide containing titanium oxide, indium tin oxidecontaining titanium oxide, or the like can be used.

Further, silicon oxide may be added into indium oxide containingtungsten oxide, indium zinc oxide containing tungsten oxide, indiumoxide containing titanium oxide, and indium tin oxide containingtitanium oxide. In a sputtering method where a thin film is formed bysputtering a target, unevenness called a nodule is generated on a targetsurface to which sputtering is performed. When a target having such anuneven shape is used, a film with uniform composition cannot be formed,a large lump of a material is generated like a dust in the film, and adense film cannot be obtained. When sputtering is performed by using atarget in which silicon oxide is added into a transparent conductivematerial as described above, unevenness on the target surface can bereduced, and a uniform and dense film can be obtained.

An example of a composition ratio of each light-transmitting conductivematerial is described. In indium oxide containing tungsten oxide, thecomposition ratio of tungsten oxide may be 1.0 wt % and indium oxide maybe 99.0 wt %. In indium zinc oxide containing tungsten oxide, tungstenoxide may be 1.0 wt %, zinc oxide may be 0.5 wt %, and indium oxide maybe 98.5 wt %. In indium oxide containing titanium oxide, titanium oxidemay be 1.0 to 5.0 wt % and indium oxide may be 99.0 to 95.0 wt %. Inindium tin oxide (ITO), tin oxide may be 10.0 wt % and indium oxide maybe 90.0 wt %. In indium zinc oxide (IZO), zinc oxide may be 10.7 wt %and indium oxide may be 89.3 wt %. Further, in indium tin oxidecontaining titanium oxide, titanium oxide may be 5.0 wt %, tin oxide maybe 10.0 wt %, and indium oxide may be 85.0 wt %. The composition ratiosas described above are just examples, and a composition ratio may be setappropriately.

In this embodiment mode, the electrode layer is formed by using indiumzinc oxide containing silicon oxide and tungsten oxide by a sputteringmethod using a gas containing water (H₂O) or H₂. In this embodimentmode, a gas containing 50 scan of argon (Ar), 1.0 sccm of oxygen (O₂),and 0.2 sccm of H₂ is used. In a case of using an H₂O gas, the flow rateis preferably 0.5 sccm or less. The indium zinc oxide film containingsilicon oxide and tungsten oxide formed in this embodiment mode hasfavorable processability, and can be etched without leaving a residue bywet etching using an etchant such as weak acid.

In addition, when an insulating layer formed by a sputtering method isprovided between the electroluminescent layer and the electrode layer(the first electrode layer or the second electrode layer, or boththereof) in the light-emitting element in this embodiment mode, thefirst electrode layer can be formed by sputtering as in the presentinvention and the insulating layer can also be formed continuously bysputtering. In such a case, since the first electrode layer and theinsulating layer can be formed without breaking vacuum, an interface canbe kept clean and contamination can be prevented. Further, since thefirst electrode layer is a film having high planarity with fewer etchingdefects, coverage of the electroluminescent layer that is stacked isfavorable. Therefore, the electroluminescent layer can be thinner, andfurther, light extraction efficiency is improved because alight-transmitting property is enhanced.

This embodiment mode can be arbitrarily combined with the otherembodiment modes described above.

When the electrode layer of the light-emitting element is manufacturedby using the present invention, that is, an indium zinc oxide filmcontaining silicon oxide and tungsten oxide that is a light-transmittingelectrode is manufactured by using a gas containing an H₂O gas or an H₂gas, a film can be obtained, which has high transmittance in a visiblelight region, low resistivity, and favorable processability. By usingsuch a film for a pixel electrode of a display device, a highly reliabledisplay device can be manufactured, in which light extraction efficiencyof a light-emitting element is favorable and defects due to an etchingdefect of an electrode or the like are suppressed.

Embodiment 1

In this embodiment, a measurement result of characteristics of an indiumzinc oxide film containing tungsten oxide that is used as an electrodelayer in the present invention will be shown.

An indium zinc oxide film containing tungsten oxide (hereafter alsoreferred to as an IWZO film) was formed by using indium zinc oxidecontaining tungsten oxide as a target by sputtering. The film formationcondition is as follows: pressure is 0.4 Pa, and as for a gas that isused, the flow rate of an argon gas is 50 sccm, the flow rate of oxygenis 1.0 sccm, and the flow rate of an H₂O gas is changed, such as 0.5sccm, 0.2 sccm, 0.25 sccm, and 0.1 sccm. Then, characteristics of eachsample were examined.

The samples were heated at 320° C. for one hour after being formed. Thisis because, by considering an actual step, there is a case of performinga heating step after a pixel electrode is formed. FIG. 28 showstransmittance with respect to a wavelength of each IWZO film formed bythe condition of the H₂O gas flow rate of 0.5 sccm, 0.2 sccm, 0.25 sccm,or 0.1 sccm. Each IWZO film formed by the condition of the H₂O gas flowrate of 0.5 sccm, 0.2 sccm, 0.25 sccm, or 0.1 sccm showed hightransmittance from 80 to 90% in a visible light wavelength region.Therefore, it was confirmed that light extraction efficiency is highwithout shielding or absorbing visible light when the film is used as apixel electrode because visible light emitted from a light-emittingelement can be transmitted well.

FIG. 27 shows resistivity of each IWZO film formed by the condition ofthe H₂O gas flow rate of 0.5 sccm, 0.2 sccm, 0.25 sccm, or 0.1 sccm. Inthe IWZO film, resistivity became higher as the H₂O gas flow rate wasincreased. When the H₂O gas flow rate is 0.25 sccm or lower, theresistivity is preferable for a pixel electrode.

An IWZO film formed without adding an H₂O gas and an IWZO film formed bythe condition of the H₂O gas flow rate of 0.5 sccm were processed by wetetching using weak acid, and processability was examined. FIGS. 25 and26 show SEM photographs by observation using a scanning electronmicroscope (SEM) after the processing. In FIG. 26, the IWZO film thatwas formed without adding an H₂O gas is shown, and the film is notsufficiently etched and a residue is still observed. On the other hand,in FIG. 25, the IWZO film that was formed by adding an H₂O gas is shown,and the film is sufficiently etched without a residue, and thus, it wasconfirmed that the film was precisely processed. Therefore, the IWZOfilm that is formed by adding an H₂O gas has favorable processability.

According to the results, when an IWZO film is formed by a sputteringmethod, processability of the obtained IWZO film is favorable by addingan H₂O gas. In a case where, as for a gas to be used, the flow rate ofan argon gas is 50 sccm and the flow rate of oxygen is 1.0 sccm,resistivity can be lowered when the flow rate of an added H₂O gas ismade to be 0.25 sccm or lower. From the results of this experiment, itis confirmed that, in a preferable gas for forming an IWZO film by asputtering method, the flow rate of an argon gas is 50 sccm, the flowrate of oxygen is 1.0 sccm, and the flow rate of an H₂O gas is 0.2 sccm.

Therefore, when an indium zinc oxide film containing tungsten oxide isformed as a light-transmitting electrode using a gas containing an H₂Ogas, a film can be obtained, which has high transmittance in a visiblelight region, low resistivity, and favorable processability. By usingsuch a film for a pixel electrode of a display device, a highly reliabledisplay device can be manufactured, in which light extraction efficiencyof a light-emitting element is favorable and defects due to an etchingdefect of an electrode or the like are suppressed.

This application is based on Japanese Patent Application serial no.2005-141899 filed on May 13, 2005, in Japan Patent Office, the entirecontents of which are hereby incorporated by reference.

What is claimed is:
 1. A display device comprising: a first insulatinglayer comprising a resin; a second insulating layer comprising a siliconnitride oxide film over and in contact with the first insulating layer;a titanium nitride film over and in contact with the second insulatinglayer; a reflective electrode layer over and in contact with thetitanium nitride film; a first electrode layer over the reflectiveelectrode layer; an electroluminescent layer over the first electrodelayer; and a second electrode layer over the electroluminescent layer,wherein in a cross section, outermost side end portions of the secondinsulating layer, the titanium nitride film, and the reflectiveelectrode layer are aligned with one another.
 2. The display deviceaccording to claim 1, wherein an entirety of a portion of theelectroluminescent layer overlaps the reflective electrode layer, andwherein the portion of the electroluminescent layer is in contact withthe first electrode layer.
 3. The display device according to claim 1,further comprising a transistor electrically connected to the reflectiveelectrode layer.
 4. The display device according to claim 1, wherein thefirst electrode layer includes comprises indium zinc oxide containingtungsten oxide.
 5. The display device according to claim 1, wherein thefirst electrode layer includes comprises indium zinc oxide containingsilicon oxide and tungsten oxide.
 6. The display device according toclaim 1, wherein the second electrode layer includes comprises indiumzinc oxide containing tungsten oxide.
 7. The display device according toclaim 1, wherein the second electrode layer includes comprises indiumzinc oxide containing silicon oxide and tungsten oxide.
 8. The displaydevice according to claim 1, wherein the reflective electrode layerincludes titanium, tungsten, nickel, gold, platinum, silver, aluminum,magnesium, calcium, lithium, or an alloy thereof.
 9. The display deviceaccording to claim 1, wherein the electroluminescent layer includes alayer containing an organic compound and an inorganic compound to be incontact with the first electrode layer.
 10. The display device accordingto claim 1, wherein a top surface of the reflective electrode layer iscovered by the first electrode layer in a region where light emittedfrom the electroluminescent layer is extracted.